text: /*-------------------------------------------------------------------------
   *
   * postmaster.c
   *	  This program acts as a clearing house for requests to the
   *	  POSTGRES system.  Frontend programs send a startup message
   *	  to the Postmaster and the postmaster uses the info in the
   *	  message to setup a backend process.
   *
   *	  The postmaster also manages system-wide operations such as
   *	  startup and shutdown. The postmaster itself doesn't do those
   *	  operations, mind you --- it just forks off a subprocess to do them
   *	  at the right times.  It also takes care of resetting the system
   *	  if a backend crashes.
   *
   *	  The postmaster process creates the shared memory and semaphore
   *	  pools during startup, but as a rule does not touch them itself.
   *	  In particular, it is not a member of the PGPROC array of backends
   *	  and so it cannot participate in lock-manager operations.  Keeping
   *	  the postmaster away from shared memory operations makes it simpler
   *	  and more reliable.  The postmaster is almost always able to recover
   *	  from crashes of individual backends by resetting shared memory;
   *	  if it did much with shared memory then it would be prone to crashing
   *	  along with the backends.
   *
   *	  When a request message is received, we now fork() immediately.
   *	  The child process performs authentication of the request, and
   *	  then becomes a backend if successful.  This allows the auth code
   *	  to be written in a simple single-threaded style (as opposed to the
   *	  crufty "poor man's multitasking" code that used to be needed).
   *	  More importantly, it ensures that blockages in non-multithreaded
   *	  libraries like SSL or PAM cannot cause denial of service to other
   *	  clients.
   *
   *
   * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/postmaster/postmaster.c
   *
   * NOTES
   *
   * Initialization:
   *		The Postmaster sets up shared memory data structures
   *		for the backends.
   *
   * Synchronization:
   *		The Postmaster shares memory with the backends but should avoid
   *		touching shared memory, so as not to become stuck if a crashing
   *		backend screws up locks or shared memory.  Likewise, the Postmaster
   *		should never block on messages from frontend clients.
   *
   * Garbage Collection:
   *		The Postmaster cleans up after backends if they have an emergency
   *		exit and/or core dump.
   *
   * Error Reporting:
   *		Use write_stderr() only for reporting "interactive" errors
   *		(essentially, bogus arguments on the command line).  Once the
   *		postmaster is launched, use ereport().
   *
   *-------------------------------------------------------------------------
   */
  
  #include "postgres.h"
  
  #include <unistd.h>
  #include <signal.h>
  #include <time.h>
  #include <sys/wait.h>
  #include <ctype.h>
  #include <sys/stat.h>
  #include <sys/socket.h>
  #include <fcntl.h>
  #include <sys/param.h>
  #include <netdb.h>
  #include <limits.h>
  
  #ifdef HAVE_SYS_SELECT_H
  #include <sys/select.h>
  #endif
  
  #ifdef USE_BONJOUR
  #include <dns_sd.h>
  #endif
  
  #ifdef USE_SYSTEMD
  #include <systemd/sd-daemon.h>
  #endif
  
  #ifdef HAVE_PTHREAD_IS_THREADED_NP
  #include <pthread.h>
  #endif
  
  #include "access/transam.h"
  #include "access/xlog.h"
  #include "access/xlogrecovery.h"
  #include "catalog/pg_control.h"
  #include "common/file_perm.h"
  #include "common/ip.h"
  #include "common/pg_prng.h"
  #include "common/string.h"
  #include "lib/ilist.h"
  #include "libpq/auth.h"
  #include "libpq/libpq.h"
  #include "libpq/pqformat.h"
  #include "libpq/pqsignal.h"
  #include "pg_getopt.h"
  #include "pgstat.h"
  #include "port/pg_bswap.h"
  #include "postmaster/autovacuum.h"
  #include "postmaster/auxprocess.h"
  #include "postmaster/bgworker_internals.h"
  #include "postmaster/fork_process.h"
  #include "postmaster/interrupt.h"
  #include "postmaster/pgarch.h"
  #include "postmaster/postmaster.h"
  #include "postmaster/syslogger.h"
  #include "replication/logicallauncher.h"
  #include "replication/walsender.h"
  #include "storage/fd.h"
  #include "storage/ipc.h"
  #include "storage/pg_shmem.h"
  #include "storage/pmsignal.h"
  #include "storage/proc.h"
  #include "tcop/tcopprot.h"
  #include "utils/builtins.h"
  #include "utils/datetime.h"
  #include "utils/memutils.h"
  #include "utils/pidfile.h"
  #include "utils/ps_status.h"
  #include "utils/queryjumble.h"
  #include "utils/timeout.h"
  #include "utils/timestamp.h"
  #include "utils/varlena.h"
  
  #ifdef EXEC_BACKEND
  #include "storage/spin.h"
  #endif
  
  
  /*
   * Possible types of a backend. Beyond being the possible bkend_type values in
   * struct bkend, these are OR-able request flag bits for SignalSomeChildren()
   * and CountChildren().
   */
  #define BACKEND_TYPE_NORMAL		0x0001	/* normal backend */
  #define BACKEND_TYPE_AUTOVAC	0x0002	/* autovacuum worker process */
  #define BACKEND_TYPE_WALSND		0x0004	/* walsender process */
  #define BACKEND_TYPE_BGWORKER	0x0008	/* bgworker process */
  #define BACKEND_TYPE_ALL		0x000F	/* OR of all the above */
  
  /*
   * List of active backends (or child processes anyway; we don't actually
   * know whether a given child has become a backend or is still in the
   * authorization phase).  This is used mainly to keep track of how many
   * children we have and send them appropriate signals when necessary.
   *
   * As shown in the above set of backend types, this list includes not only
   * "normal" client sessions, but also autovacuum workers, walsenders, and
   * background workers.  (Note that at the time of launch, walsenders are
   * labeled BACKEND_TYPE_NORMAL; we relabel them to BACKEND_TYPE_WALSND
   * upon noticing they've changed their PMChildFlags entry.  Hence that check
   * must be done before any operation that needs to distinguish walsenders
   * from normal backends.)
   *
   * Also, "dead_end" children are in it: these are children launched just for
   * the purpose of sending a friendly rejection message to a would-be client.
   * We must track them because they are attached to shared memory, but we know
   * they will never become live backends.  dead_end children are not assigned a
   * PMChildSlot.  dead_end children have bkend_type NORMAL.
   *
   * "Special" children such as the startup, bgwriter and autovacuum launcher
   * tasks are not in this list.  They are tracked via StartupPID and other
   * pid_t variables below.  (Thus, there can't be more than one of any given
   * "special" child process type.  We use BackendList entries for any child
   * process there can be more than one of.)
   */
  typedef struct bkend
  {
  	pid_t		pid;			/* process id of backend */
  	int32		cancel_key;		/* cancel key for cancels for this backend */
  	int			child_slot;		/* PMChildSlot for this backend, if any */
  	int			bkend_type;		/* child process flavor, see above */
  	bool		dead_end;		/* is it going to send an error and quit? */
  	bool		bgworker_notify;	/* gets bgworker start/stop notifications */
  	dlist_node	elem;			/* list link in BackendList */
  } Backend;
  
  static dlist_head BackendList = DLIST_STATIC_INIT(BackendList);
  
  #ifdef EXEC_BACKEND
  static Backend *ShmemBackendArray;
  #endif
  
  BackgroundWorker *MyBgworkerEntry = NULL;
  
  
  
  /* The socket number we are listening for connections on */
  int			PostPortNumber;
  
  /* The directory names for Unix socket(s) */
  char	   *Unix_socket_directories;
  
  /* The TCP listen address(es) */
  char	   *ListenAddresses;
  
  /*
   * ReservedBackends is the number of backends reserved for superuser use.
   * This number is taken out of the pool size given by MaxConnections so
   * number of backend slots available to non-superusers is
   * (MaxConnections - ReservedBackends).  Note what this really means is
   * "if there are <= ReservedBackends connections available, only superusers
   * can make new connections" --- pre-existing superuser connections don't
   * count against the limit.
   */
  int			ReservedBackends;
  
  /* The socket(s) we're listening to. */
  #define MAXLISTEN	64
  static pgsocket ListenSocket[MAXLISTEN];
  
  /*
   * These globals control the behavior of the postmaster in case some
   * backend dumps core.  Normally, it kills all peers of the dead backend
   * and reinitializes shared memory.  By specifying -s or -n, we can have
   * the postmaster stop (rather than kill) peers and not reinitialize
   * shared data structures.  (Reinit is currently dead code, though.)
   */
  static bool Reinit = true;
  static int	SendStop = false;
  
  /* still more option variables */
  bool		EnableSSL = false;
  
  int			PreAuthDelay = 0;
  int			AuthenticationTimeout = 60;
  
  bool		log_hostname;		/* for ps display and logging */
  bool		Log_connections = false;
  bool		Db_user_namespace = false;
  
  bool		enable_bonjour = false;
  char	   *bonjour_name;
  bool		restart_after_crash = true;
  bool		remove_temp_files_after_crash = true;
  
  /* PIDs of special child processes; 0 when not running */
  static pid_t StartupPID = 0,
  			BgWriterPID = 0,
  			CheckpointerPID = 0,
  			WalWriterPID = 0,
  			WalReceiverPID = 0,
  			AutoVacPID = 0,
  			PgArchPID = 0,
  			SysLoggerPID = 0;
  
  /* Startup process's status */
  typedef enum
  {
  	STARTUP_NOT_RUNNING,
  	STARTUP_RUNNING,
  	STARTUP_SIGNALED,			/* we sent it a SIGQUIT or SIGKILL */
  	STARTUP_CRASHED
  } StartupStatusEnum;
  
  static StartupStatusEnum StartupStatus = STARTUP_NOT_RUNNING;
  
  /* Startup/shutdown state */
  #define			NoShutdown		0
  #define			SmartShutdown	1
  #define			FastShutdown	2
  #define			ImmediateShutdown	3
  
  static int	Shutdown = NoShutdown;
  
  static bool FatalError = false; /* T if recovering from backend crash */
  
  /*
   * We use a simple state machine to control startup, shutdown, and
   * crash recovery (which is rather like shutdown followed by startup).
   *
   * After doing all the postmaster initialization work, we enter PM_STARTUP
   * state and the startup process is launched. The startup process begins by
   * reading the control file and other preliminary initialization steps.
   * In a normal startup, or after crash recovery, the startup process exits
   * with exit code 0 and we switch to PM_RUN state.  However, archive recovery
   * is handled specially since it takes much longer and we would like to support
   * hot standby during archive recovery.
   *
   * When the startup process is ready to start archive recovery, it signals the
   * postmaster, and we switch to PM_RECOVERY state. The background writer and
   * checkpointer are launched, while the startup process continues applying WAL.
   * If Hot Standby is enabled, then, after reaching a consistent point in WAL
   * redo, startup process signals us again, and we switch to PM_HOT_STANDBY
   * state and begin accepting connections to perform read-only queries.  When
   * archive recovery is finished, the startup process exits with exit code 0
   * and we switch to PM_RUN state.
   *
   * Normal child backends can only be launched when we are in PM_RUN or
   * PM_HOT_STANDBY state.  (connsAllowed can also restrict launching.)
   * In other states we handle connection requests by launching "dead_end"
   * child processes, which will simply send the client an error message and
   * quit.  (We track these in the BackendList so that we can know when they
   * are all gone; this is important because they're still connected to shared
   * memory, and would interfere with an attempt to destroy the shmem segment,
   * possibly leading to SHMALL failure when we try to make a new one.)
   * In PM_WAIT_DEAD_END state we are waiting for all the dead_end children
   * to drain out of the system, and therefore stop accepting connection
   * requests at all until the last existing child has quit (which hopefully
   * will not be very long).
   *
   * Notice that this state variable does not distinguish *why* we entered
   * states later than PM_RUN --- Shutdown and FatalError must be consulted
   * to find that out.  FatalError is never true in PM_RECOVERY, PM_HOT_STANDBY,
   * or PM_RUN states, nor in PM_SHUTDOWN states (because we don't enter those
   * states when trying to recover from a crash).  It can be true in PM_STARTUP
   * state, because we don't clear it until we've successfully started WAL redo.
   */
  typedef enum
  {
  	PM_INIT,					/* postmaster starting */
  	PM_STARTUP,					/* waiting for startup subprocess */
  	PM_RECOVERY,				/* in archive recovery mode */
  	PM_HOT_STANDBY,				/* in hot standby mode */
  	PM_RUN,						/* normal "database is alive" state */
  	PM_STOP_BACKENDS,			/* need to stop remaining backends */
  	PM_WAIT_BACKENDS,			/* waiting for live backends to exit */
  	PM_SHUTDOWN,				/* waiting for checkpointer to do shutdown
  								 * ckpt */
  	PM_SHUTDOWN_2,				/* waiting for archiver and walsenders to
  								 * finish */
  	PM_WAIT_DEAD_END,			/* waiting for dead_end children to exit */
  	PM_NO_CHILDREN				/* all important children have exited */
  } PMState;
  
  static PMState pmState = PM_INIT;
  
  /*
   * While performing a "smart shutdown", we restrict new connections but stay
   * in PM_RUN or PM_HOT_STANDBY state until all the client backends are gone.
   * connsAllowed is a sub-state indicator showing the active restriction.
   * It is of no interest unless pmState is PM_RUN or PM_HOT_STANDBY.
   */
  static bool connsAllowed = true;
  
  /* Start time of SIGKILL timeout during immediate shutdown or child crash */
  /* Zero means timeout is not running */
  static time_t AbortStartTime = 0;
  
  /* Length of said timeout */
  #define SIGKILL_CHILDREN_AFTER_SECS		5
  
  static bool ReachedNormalRunning = false;	/* T if we've reached PM_RUN */
  
  bool		ClientAuthInProgress = false;	/* T during new-client
  											 * authentication */
  
  bool		redirection_done = false;	/* stderr redirected for syslogger? */
  
  /* received START_AUTOVAC_LAUNCHER signal */
  static volatile sig_atomic_t start_autovac_launcher = false;
  
  /* the launcher needs to be signaled to communicate some condition */
  static volatile bool avlauncher_needs_signal = false;
  
  /* received START_WALRECEIVER signal */
  static volatile sig_atomic_t WalReceiverRequested = false;
  
  /* set when there's a worker that needs to be started up */
  static volatile bool StartWorkerNeeded = true;
  static volatile bool HaveCrashedWorker = false;
  
  #ifdef USE_SSL
  /* Set when and if SSL has been initialized properly */
  static bool LoadedSSL = false;
  #endif
  
  #ifdef USE_BONJOUR
  static DNSServiceRef bonjour_sdref = NULL;
  #endif
  
  /*
   * postmaster.c - function prototypes
   */
  static void CloseServerPorts(int status, Datum arg);
  static void unlink_external_pid_file(int status, Datum arg);
  static void getInstallationPaths(const char *argv0);
  static void checkControlFile(void);
  static Port *ConnCreate(int serverFd);
  static void ConnFree(Port *port);
  static void reset_shared(void);
  static void SIGHUP_handler(SIGNAL_ARGS);
  static void pmdie(SIGNAL_ARGS);
  static void reaper(SIGNAL_ARGS);
  static void sigusr1_handler(SIGNAL_ARGS);
  static void process_startup_packet_die(SIGNAL_ARGS);
  static void dummy_handler(SIGNAL_ARGS);
  static void StartupPacketTimeoutHandler(void);
  static void CleanupBackend(int pid, int exitstatus);
  static bool CleanupBackgroundWorker(int pid, int exitstatus);
  static void HandleChildCrash(int pid, int exitstatus, const char *procname);
  static void LogChildExit(int lev, const char *procname,
  						 int pid, int exitstatus);
  static void PostmasterStateMachine(void);
  static void BackendInitialize(Port *port);
  static void BackendRun(Port *port) pg_attribute_noreturn();
  static void ExitPostmaster(int status) pg_attribute_noreturn();
  static int	ServerLoop(void);
  static int	BackendStartup(Port *port);
  static int	ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done);
  static void SendNegotiateProtocolVersion(List *unrecognized_protocol_options);
  static void processCancelRequest(Port *port, void *pkt);
  static int	initMasks(fd_set *rmask);
  static void report_fork_failure_to_client(Port *port, int errnum);
  static CAC_state canAcceptConnections(int backend_type);
  static bool RandomCancelKey(int32 *cancel_key);
  static void signal_child(pid_t pid, int signal);
  static bool SignalSomeChildren(int signal, int targets);
  static void TerminateChildren(int signal);
  
  #define SignalChildren(sig)			   SignalSomeChildren(sig, BACKEND_TYPE_ALL)
  
  static int	CountChildren(int target);
  static bool assign_backendlist_entry(RegisteredBgWorker *rw);
  static void maybe_start_bgworkers(void);
  static bool CreateOptsFile(int argc, char *argv[], char *fullprogname);
  static pid_t StartChildProcess(AuxProcType type);
  static void StartAutovacuumWorker(void);
  static void MaybeStartWalReceiver(void);
  static void InitPostmasterDeathWatchHandle(void);
  
  /*
   * Archiver is allowed to start up at the current postmaster state?
   *
   * If WAL archiving is enabled always, we are allowed to start archiver
   * even during recovery.
   */
  #define PgArchStartupAllowed()	\
  	(((XLogArchivingActive() && pmState == PM_RUN) ||			\
  	  (XLogArchivingAlways() &&									  \
  	   (pmState == PM_RECOVERY || pmState == PM_HOT_STANDBY))) && \
  	 PgArchCanRestart())
  
  #ifdef EXEC_BACKEND
  
  #ifdef WIN32
  #define WNOHANG 0				/* ignored, so any integer value will do */
  
  static pid_t waitpid(pid_t pid, int *exitstatus, int options);
  static void WINAPI pgwin32_deadchild_callback(PVOID lpParameter, BOOLEAN TimerOrWaitFired);
  
  static HANDLE win32ChildQueue;
  
  typedef struct
  {
  	HANDLE		waitHandle;
  	HANDLE		procHandle;
  	DWORD		procId;
  } win32_deadchild_waitinfo;
  #endif							/* WIN32 */
  
  static pid_t backend_forkexec(Port *port);
  static pid_t internal_forkexec(int argc, char *argv[], Port *port);
  
  /* Type for a socket that can be inherited to a client process */
  #ifdef WIN32
  typedef struct
  {
  	SOCKET		origsocket;		/* Original socket value, or PGINVALID_SOCKET
  								 * if not a socket */
  	WSAPROTOCOL_INFO wsainfo;
  } InheritableSocket;
  #else
  typedef int InheritableSocket;
  #endif
  
  /*
   * Structure contains all variables passed to exec:ed backends
   */
  typedef struct
  {
  	Port		port;
  	InheritableSocket portsocket;
  	char		DataDir[MAXPGPATH];
  	pgsocket	ListenSocket[MAXLISTEN];
  	int32		MyCancelKey;
  	int			MyPMChildSlot;
  #ifndef WIN32
  	unsigned long UsedShmemSegID;
  #else
  	void	   *ShmemProtectiveRegion;
  	HANDLE		UsedShmemSegID;
  #endif
  	void	   *UsedShmemSegAddr;
  	slock_t    *ShmemLock;
  	VariableCache ShmemVariableCache;
  	Backend    *ShmemBackendArray;
  #ifndef HAVE_SPINLOCKS
  	PGSemaphore *SpinlockSemaArray;
  #endif
  	int			NamedLWLockTrancheRequests;
  	NamedLWLockTranche *NamedLWLockTrancheArray;
  	LWLockPadded *MainLWLockArray;
  	slock_t    *ProcStructLock;
  	PROC_HDR   *ProcGlobal;
  	PGPROC	   *AuxiliaryProcs;
  	PGPROC	   *PreparedXactProcs;
  	PMSignalData *PMSignalState;
  	pid_t		PostmasterPid;
  	TimestampTz PgStartTime;
  	TimestampTz PgReloadTime;
  	pg_time_t	first_syslogger_file_time;
  	bool		redirection_done;
  	bool		IsBinaryUpgrade;
  	bool		query_id_enabled;
  	int			max_safe_fds;
  	int			MaxBackends;
  #ifdef WIN32
  	HANDLE		PostmasterHandle;
  	HANDLE		initial_signal_pipe;
  	HANDLE		syslogPipe[2];
  #else
  	int			postmaster_alive_fds[2];
  	int			syslogPipe[2];
  #endif
  	char		my_exec_path[MAXPGPATH];
  	char		pkglib_path[MAXPGPATH];
  } BackendParameters;
  
  static void read_backend_variables(char *id, Port *port);
  static void restore_backend_variables(BackendParameters *param, Port *port);
  
  #ifndef WIN32
  static bool save_backend_variables(BackendParameters *param, Port *port);
  #else
  static bool save_backend_variables(BackendParameters *param, Port *port,
  								   HANDLE childProcess, pid_t childPid);
  #endif
  
  static void ShmemBackendArrayAdd(Backend *bn);
  static void ShmemBackendArrayRemove(Backend *bn);
  #endif							/* EXEC_BACKEND */
  
  #define StartupDataBase()		StartChildProcess(StartupProcess)
  #define StartArchiver()			StartChildProcess(ArchiverProcess)
  #define StartBackgroundWriter() StartChildProcess(BgWriterProcess)
  #define StartCheckpointer()		StartChildProcess(CheckpointerProcess)
  #define StartWalWriter()		StartChildProcess(WalWriterProcess)
  #define StartWalReceiver()		StartChildProcess(WalReceiverProcess)
  
  /* Macros to check exit status of a child process */
  #define EXIT_STATUS_0(st)  ((st) == 0)
  #define EXIT_STATUS_1(st)  (WIFEXITED(st) && WEXITSTATUS(st) == 1)
  #define EXIT_STATUS_3(st)  (WIFEXITED(st) && WEXITSTATUS(st) == 3)
  
  #ifndef WIN32
  /*
   * File descriptors for pipe used to monitor if postmaster is alive.
   * First is POSTMASTER_FD_WATCH, second is POSTMASTER_FD_OWN.
   */
  int			postmaster_alive_fds[2] = {-1, -1};
  #else
  /* Process handle of postmaster used for the same purpose on Windows */
  HANDLE		PostmasterHandle;
  #endif
  
  /*
   * Postmaster main entry point
   */
  void
  PostmasterMain(int argc, char *argv[])
  {
  	int			opt;
  	int			status;
  	char	   *userDoption = NULL;
  	bool		listen_addr_saved = false;
  	int			i;
  	char	   *output_config_variable = NULL;
  
  	InitProcessGlobals();
  
  	PostmasterPid = MyProcPid;
  
  	IsPostmasterEnvironment = true;
  
  	/*
  	 * Start our win32 signal implementation
  	 */
  #ifdef WIN32
  	pgwin32_signal_initialize();
  #endif
  
  	/*
  	 * We should not be creating any files or directories before we check the
  	 * data directory (see checkDataDir()), but just in case set the umask to
  	 * the most restrictive (owner-only) permissions.
  	 *
  	 * checkDataDir() will reset the umask based on the data directory
  	 * permissions.
  	 */
  	umask(PG_MODE_MASK_OWNER);
  
  	/*
  	 * By default, palloc() requests in the postmaster will be allocated in
  	 * the PostmasterContext, which is space that can be recycled by backends.
  	 * Allocated data that needs to be available to backends should be
  	 * allocated in TopMemoryContext.
  	 */
  	PostmasterContext = AllocSetContextCreate(TopMemoryContext,
  											  "Postmaster",
  											  ALLOCSET_DEFAULT_SIZES);
  	MemoryContextSwitchTo(PostmasterContext);
  
  	/* Initialize paths to installation files */
  	getInstallationPaths(argv[0]);
  
  	/*
  	 * Set up signal handlers for the postmaster process.
  	 *
  	 * In the postmaster, we use pqsignal_pm() rather than pqsignal() (which
  	 * is used by all child processes and client processes).  That has a
  	 * couple of special behaviors:
  	 *
  	 * 1. Except on Windows, we tell sigaction() to block all signals for the
  	 * duration of the signal handler.  This is faster than our old approach
  	 * of blocking/unblocking explicitly in the signal handler, and it should
  	 * also prevent excessive stack consumption if signals arrive quickly.
  	 *
  	 * 2. We do not set the SA_RESTART flag.  This is because signals will be
  	 * blocked at all times except when ServerLoop is waiting for something to
  	 * happen, and during that window, we want signals to exit the select(2)
  	 * wait so that ServerLoop can respond if anything interesting happened.
  	 * On some platforms, signals marked SA_RESTART would not cause the
  	 * select() wait to end.
  	 *
  	 * Child processes will generally want SA_RESTART, so pqsignal() sets that
  	 * flag.  We expect children to set up their own handlers before
  	 * unblocking signals.
  	 *
  	 * CAUTION: when changing this list, check for side-effects on the signal
  	 * handling setup of child processes.  See tcop/postgres.c,
  	 * bootstrap/bootstrap.c, postmaster/bgwriter.c, postmaster/walwriter.c,
  	 * postmaster/autovacuum.c, postmaster/pgarch.c, postmaster/syslogger.c,
  	 * postmaster/bgworker.c and postmaster/checkpointer.c.
  	 */
  	pqinitmask();
  	PG_SETMASK(&BlockSig);
  
  	pqsignal_pm(SIGHUP, SIGHUP_handler);	/* reread config file and have
  											 * children do same */
  	pqsignal_pm(SIGINT, pmdie); /* send SIGTERM and shut down */
  	pqsignal_pm(SIGQUIT, pmdie);	/* send SIGQUIT and die */
  	pqsignal_pm(SIGTERM, pmdie);	/* wait for children and shut down */
  	pqsignal_pm(SIGALRM, SIG_IGN);	/* ignored */
  	pqsignal_pm(SIGPIPE, SIG_IGN);	/* ignored */
  	pqsignal_pm(SIGUSR1, sigusr1_handler);	/* message from child process */
  	pqsignal_pm(SIGUSR2, dummy_handler);	/* unused, reserve for children */
  	pqsignal_pm(SIGCHLD, reaper);	/* handle child termination */
  
  #ifdef SIGURG
  
  	/*
  	 * Ignore SIGURG for now.  Child processes may change this (see
  	 * InitializeLatchSupport), but they will not receive any such signals
  	 * until they wait on a latch.
  	 */
  	pqsignal_pm(SIGURG, SIG_IGN);	/* ignored */
  #endif
  
  	/*
  	 * No other place in Postgres should touch SIGTTIN/SIGTTOU handling.  We
  	 * ignore those signals in a postmaster environment, so that there is no
  	 * risk of a child process freezing up due to writing to stderr.  But for
  	 * a standalone backend, their default handling is reasonable.  Hence, all
  	 * child processes should just allow the inherited settings to stand.
  	 */
  #ifdef SIGTTIN
  	pqsignal_pm(SIGTTIN, SIG_IGN);	/* ignored */
  #endif
  #ifdef SIGTTOU
  	pqsignal_pm(SIGTTOU, SIG_IGN);	/* ignored */
  #endif
  
  	/* ignore SIGXFSZ, so that ulimit violations work like disk full */
  #ifdef SIGXFSZ
  	pqsignal_pm(SIGXFSZ, SIG_IGN);	/* ignored */
  #endif
  
  	/*
  	 * Options setup
  	 */
  	InitializeGUCOptions();
  
  	opterr = 1;
  
  	/*
  	 * Parse command-line options.  CAUTION: keep this in sync with
  	 * tcop/postgres.c (the option sets should not conflict) and with the
  	 * common help() function in main/main.c.
  	 */
  	while ((opt = getopt(argc, argv, "B:bc:C:D:d:EeFf:h:ijk:lN:nOPp:r:S:sTt:W:-:")) != -1)
  	{
  		switch (opt)
  		{
  			case 'B':
  				SetConfigOption("shared_buffers", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'b':
  				/* Undocumented flag used for binary upgrades */
  				IsBinaryUpgrade = true;
  				break;
  
  			case 'C':
  				output_config_variable = strdup(optarg);
  				break;
  
  			case 'D':
  				userDoption = strdup(optarg);
  				break;
  
  			case 'd':
  				set_debug_options(atoi(optarg), PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'E':
  				SetConfigOption("log_statement", "all", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'e':
  				SetConfigOption("datestyle", "euro", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'F':
  				SetConfigOption("fsync", "false", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'f':
  				if (!set_plan_disabling_options(optarg, PGC_POSTMASTER, PGC_S_ARGV))
  				{
  					write_stderr("%s: invalid argument for option -f: \"%s\"\n",
  								 progname, optarg);
  					ExitPostmaster(1);
  				}
  				break;
  
  			case 'h':
  				SetConfigOption("listen_addresses", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'i':
  				SetConfigOption("listen_addresses", "*", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'j':
  				/* only used by interactive backend */
  				break;
  
  			case 'k':
  				SetConfigOption("unix_socket_directories", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'l':
  				SetConfigOption("ssl", "true", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'N':
  				SetConfigOption("max_connections", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'n':
  				/* Don't reinit shared mem after abnormal exit */
  				Reinit = false;
  				break;
  
  			case 'O':
  				SetConfigOption("allow_system_table_mods", "true", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'P':
  				SetConfigOption("ignore_system_indexes", "true", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'p':
  				SetConfigOption("port", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'r':
  				/* only used by single-user backend */
  				break;
  
  			case 'S':
  				SetConfigOption("work_mem", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 's':
  				SetConfigOption("log_statement_stats", "true", PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'T':
  
  				/*
  				 * In the event that some backend dumps core, send SIGSTOP,
  				 * rather than SIGQUIT, to all its peers.  This lets the wily
  				 * post_hacker collect core dumps from everyone.
  				 */
  				SendStop = true;
  				break;
  
  			case 't':
  				{
  					const char *tmp = get_stats_option_name(optarg);
  
  					if (tmp)
  					{
  						SetConfigOption(tmp, "true", PGC_POSTMASTER, PGC_S_ARGV);
  					}
  					else
  					{
  						write_stderr("%s: invalid argument for option -t: \"%s\"\n",
  									 progname, optarg);
  						ExitPostmaster(1);
  					}
  					break;
  				}
  
  			case 'W':
  				SetConfigOption("post_auth_delay", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			case 'c':
  			case '-':
  				{
  					char	   *name,
  							   *value;
  
  					ParseLongOption(optarg, &name, &value);
  					if (!value)
  					{
  						if (opt == '-')
  							ereport(ERROR,
  									(errcode(ERRCODE_SYNTAX_ERROR),
  									 errmsg("--%s requires a value",
  											optarg)));
  						else
  							ereport(ERROR,
  									(errcode(ERRCODE_SYNTAX_ERROR),
  									 errmsg("-c %s requires a value",
  											optarg)));
  					}
  
  					SetConfigOption(name, value, PGC_POSTMASTER, PGC_S_ARGV);
  					free(name);
  					if (value)
  						free(value);
  					break;
  				}
  
  			default:
  				write_stderr("Try \"%s --help\" for more information.\n",
  							 progname);
  				ExitPostmaster(1);
  		}
  	}
  
  	/*
  	 * Postmaster accepts no non-option switch arguments.
  	 */
  	if (optind < argc)
  	{
  		write_stderr("%s: invalid argument: \"%s\"\n",
  					 progname, argv[optind]);
  		write_stderr("Try \"%s --help\" for more information.\n",
  					 progname);
  		ExitPostmaster(1);
  	}
  
  	/*
  	 * Locate the proper configuration files and data directory, and read
  	 * postgresql.conf for the first time.
  	 */
  	if (!SelectConfigFiles(userDoption, progname))
  		ExitPostmaster(2);
  
  	if (output_config_variable != NULL)
  	{
  		/*
  		 * If this is a runtime-computed GUC, it hasn't yet been initialized,
  		 * and the present value is not useful.  However, this is a convenient
  		 * place to print the value for most GUCs because it is safe to run
  		 * postmaster startup to this point even if the server is already
  		 * running.  For the handful of runtime-computed GUCs that we cannot
  		 * provide meaningful values for yet, we wait until later in
  		 * postmaster startup to print the value.  We won't be able to use -C
  		 * on running servers for those GUCs, but using this option now would
  		 * lead to incorrect results for them.
  		 */
  		int			flags = GetConfigOptionFlags(output_config_variable, true);
  
  		if ((flags & GUC_RUNTIME_COMPUTED) == 0)
  		{
  			/*
  			 * "-C guc" was specified, so print GUC's value and exit.  No
  			 * extra permission check is needed because the user is reading
  			 * inside the data dir.
  			 */
  			const char *config_val = GetConfigOption(output_config_variable,
  													 false, false);
  
  			puts(config_val ? config_val : "");
  			ExitPostmaster(0);
  		}
  	}
  
  	/* Verify that DataDir looks reasonable */
  	checkDataDir();
  
  	/* Check that pg_control exists */
  	checkControlFile();
  
  	/* And switch working directory into it */
  	ChangeToDataDir();
  
  	/*
  	 * Check for invalid combinations of GUC settings.
  	 */
  	if (ReservedBackends >= MaxConnections)
  	{
  		write_stderr("%s: superuser_reserved_connections (%d) must be less than max_connections (%d)\n",
  					 progname,
  					 ReservedBackends, MaxConnections);
  		ExitPostmaster(1);
  	}
  	if (XLogArchiveMode > ARCHIVE_MODE_OFF && wal_level == WAL_LEVEL_MINIMAL)
  		ereport(ERROR,
  				(errmsg("WAL archival cannot be enabled when wal_level is \"minimal\"")));
  	if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL)
  		ereport(ERROR,
  				(errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"replica\" or \"logical\"")));
  
  	/*
  	 * Other one-time internal sanity checks can go here, if they are fast.
  	 * (Put any slow processing further down, after postmaster.pid creation.)
  	 */
  	if (!CheckDateTokenTables())
  	{
  		write_stderr("%s: invalid datetoken tables, please fix\n", progname);
  		ExitPostmaster(1);
  	}
  
  	/*
  	 * Now that we are done processing the postmaster arguments, reset
  	 * getopt(3) library so that it will work correctly in subprocesses.
  	 */
  	optind = 1;
  #ifdef HAVE_INT_OPTRESET
  	optreset = 1;				/* some systems need this too */
  #endif
  
  	/* For debugging: display postmaster environment */
  	{
  		extern char **environ;
  		char	  **p;
  
  		ereport(DEBUG3,
  				(errmsg_internal("%s: PostmasterMain: initial environment dump:",
  								 progname)));
  		ereport(DEBUG3,
  				(errmsg_internal("-----------------------------------------")));
  		for (p = environ; *p; ++p)
  			ereport(DEBUG3,
  					(errmsg_internal("\t%s", *p)));
  		ereport(DEBUG3,
  				(errmsg_internal("-----------------------------------------")));
  	}
  
  	/*
  	 * Create lockfile for data directory.
  	 *
  	 * We want to do this before we try to grab the input sockets, because the
  	 * data directory interlock is more reliable than the socket-file
  	 * interlock (thanks to whoever decided to put socket files in /tmp :-().
  	 * For the same reason, it's best to grab the TCP socket(s) before the
  	 * Unix socket(s).
  	 *
  	 * Also note that this internally sets up the on_proc_exit function that
  	 * is responsible for removing both data directory and socket lockfiles;
  	 * so it must happen before opening sockets so that at exit, the socket
  	 * lockfiles go away after CloseServerPorts runs.
  	 */
  	CreateDataDirLockFile(true);
  
  	/*
  	 * Read the control file (for error checking and config info).
  	 *
  	 * Since we verify the control file's CRC, this has a useful side effect
  	 * on machines where we need a run-time test for CRC support instructions.
  	 * The postmaster will do the test once at startup, and then its child
  	 * processes will inherit the correct function pointer and not need to
  	 * repeat the test.
  	 */
  	LocalProcessControlFile(false);
  
  	/*
  	 * Register the apply launcher.  It's probably a good idea to call this
  	 * before any modules had a chance to take the background worker slots.
  	 */
  	ApplyLauncherRegister();
  
  	/*
  	 * process any libraries that should be preloaded at postmaster start
  	 */
  	process_shared_preload_libraries();
  
  	/*
  	 * Initialize SSL library, if specified.
  	 */
  #ifdef USE_SSL
  	if (EnableSSL)
  	{
  		(void) secure_initialize(true);
  		LoadedSSL = true;
  	}
  #endif
  
  	/*
  	 * Now that loadable modules have had their chance to alter any GUCs,
  	 * calculate MaxBackends.
  	 */
  	InitializeMaxBackends();
  
  	/*
  	 * Now that loadable modules have had their chance to request additional
  	 * shared memory, determine the value of any runtime-computed GUCs that
  	 * depend on the amount of shared memory required.
  	 */
  	InitializeShmemGUCs();
  
  	/*
  	 * Now that modules have been loaded, we can process any custom resource
  	 * managers specified in the wal_consistency_checking GUC.
  	 */
  	InitializeWalConsistencyChecking();
  
  	/*
  	 * If -C was specified with a runtime-computed GUC, we held off printing
  	 * the value earlier, as the GUC was not yet initialized.  We handle -C
  	 * for most GUCs before we lock the data directory so that the option may
  	 * be used on a running server.  However, a handful of GUCs are runtime-
  	 * computed and do not have meaningful values until after locking the data
  	 * directory, and we cannot safely calculate their values earlier on a
  	 * running server.  At this point, such GUCs should be properly
  	 * initialized, and we haven't yet set up shared memory, so this is a good
  	 * time to handle the -C option for these special GUCs.
  	 */
  	if (output_config_variable != NULL)
  	{
  		const char *config_val = GetConfigOption(output_config_variable,
  												 false, false);
  
  		puts(config_val ? config_val : "");
  		ExitPostmaster(0);
  	}
  
  	/*
  	 * Set up shared memory and semaphores.
  	 */
  	reset_shared();
  
  	/*
  	 * Estimate number of openable files.  This must happen after setting up
  	 * semaphores, because on some platforms semaphores count as open files.
  	 */
  	set_max_safe_fds();
  
  	/*
  	 * Set reference point for stack-depth checking.
  	 */
  	(void) set_stack_base();
  
  	/*
  	 * Initialize pipe (or process handle on Windows) that allows children to
  	 * wake up from sleep on postmaster death.
  	 */
  	InitPostmasterDeathWatchHandle();
  
  #ifdef WIN32
  
  	/*
  	 * Initialize I/O completion port used to deliver list of dead children.
  	 */
  	win32ChildQueue = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 1);
  	if (win32ChildQueue == NULL)
  		ereport(FATAL,
  				(errmsg("could not create I/O completion port for child queue")));
  #endif
  
  #ifdef EXEC_BACKEND
  	/* Write out nondefault GUC settings for child processes to use */
  	write_nondefault_variables(PGC_POSTMASTER);
  
  	/*
  	 * Clean out the temp directory used to transmit parameters to child
  	 * processes (see internal_forkexec, below).  We must do this before
  	 * launching any child processes, else we have a race condition: we could
  	 * remove a parameter file before the child can read it.  It should be
  	 * safe to do so now, because we verified earlier that there are no
  	 * conflicting Postgres processes in this data directory.
  	 */
  	RemovePgTempFilesInDir(PG_TEMP_FILES_DIR, true, false);
  #endif
  
  	/*
  	 * Forcibly remove the files signaling a standby promotion request.
  	 * Otherwise, the existence of those files triggers a promotion too early,
  	 * whether a user wants that or not.
  	 *
  	 * This removal of files is usually unnecessary because they can exist
  	 * only during a few moments during a standby promotion. However there is
  	 * a race condition: if pg_ctl promote is executed and creates the files
  	 * during a promotion, the files can stay around even after the server is
  	 * brought up to be the primary.  Then, if a new standby starts by using
  	 * the backup taken from the new primary, the files can exist at server
  	 * startup and must be removed in order to avoid an unexpected promotion.
  	 *
  	 * Note that promotion signal files need to be removed before the startup
  	 * process is invoked. Because, after that, they can be used by
  	 * postmaster's SIGUSR1 signal handler.
  	 */
  	RemovePromoteSignalFiles();
  
  	/* Do the same for logrotate signal file */
  	RemoveLogrotateSignalFiles();
  
  	/* Remove any outdated file holding the current log filenames. */
  	if (unlink(LOG_METAINFO_DATAFILE) < 0 && errno != ENOENT)
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not remove file \"%s\": %m",
  						LOG_METAINFO_DATAFILE)));
  
  	/*
  	 * If enabled, start up syslogger collection subprocess
  	 */
  	SysLoggerPID = SysLogger_Start();
  
  	/*
  	 * Reset whereToSendOutput from DestDebug (its starting state) to
  	 * DestNone. This stops ereport from sending log messages to stderr unless
  	 * Log_destination permits.  We don't do this until the postmaster is
  	 * fully launched, since startup failures may as well be reported to
  	 * stderr.
  	 *
  	 * If we are in fact disabling logging to stderr, first emit a log message
  	 * saying so, to provide a breadcrumb trail for users who may not remember
  	 * that their logging is configured to go somewhere else.
  	 */
  	if (!(Log_destination & LOG_DESTINATION_STDERR))
  		ereport(LOG,
  				(errmsg("ending log output to stderr"),
  				 errhint("Future log output will go to log destination \"%s\".",
  						 Log_destination_string)));
  
  	whereToSendOutput = DestNone;
  
  	/*
  	 * Report server startup in log.  While we could emit this much earlier,
  	 * it seems best to do so after starting the log collector, if we intend
  	 * to use one.
  	 */
  	ereport(LOG,
  			(errmsg("starting %s", PG_VERSION_STR)));
  
  	/*
  	 * Establish input sockets.
  	 *
  	 * First, mark them all closed, and set up an on_proc_exit function that's
  	 * charged with closing the sockets again at postmaster shutdown.
  	 */
  	for (i = 0; i < MAXLISTEN; i++)
  		ListenSocket[i] = PGINVALID_SOCKET;
  
  	on_proc_exit(CloseServerPorts, 0);
  
  	if (ListenAddresses)
  	{
  		char	   *rawstring;
  		List	   *elemlist;
  		ListCell   *l;
  		int			success = 0;
  
  		/* Need a modifiable copy of ListenAddresses */
  		rawstring = pstrdup(ListenAddresses);
  
  		/* Parse string into list of hostnames */
  		if (!SplitGUCList(rawstring, ',', &elemlist))
  		{
  			/* syntax error in list */
  			ereport(FATAL,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  					 errmsg("invalid list syntax in parameter \"%s\"",
  							"listen_addresses")));
  		}
  
  		foreach(l, elemlist)
  		{
  			char	   *curhost = (char *) lfirst(l);
  
  			if (strcmp(curhost, "*") == 0)
  				status = StreamServerPort(AF_UNSPEC, NULL,
  										  (unsigned short) PostPortNumber,
  										  NULL,
  										  ListenSocket, MAXLISTEN);
  			else
  				status = StreamServerPort(AF_UNSPEC, curhost,
  										  (unsigned short) PostPortNumber,
  										  NULL,
  										  ListenSocket, MAXLISTEN);
  
  			if (status == STATUS_OK)
  			{
  				success++;
  				/* record the first successful host addr in lockfile */
  				if (!listen_addr_saved)
  				{
  					AddToDataDirLockFile(LOCK_FILE_LINE_LISTEN_ADDR, curhost);
  					listen_addr_saved = true;
  				}
  			}
  			else
  				ereport(WARNING,
  						(errmsg("could not create listen socket for \"%s\"",
  								curhost)));
  		}
  
  		if (!success && elemlist != NIL)
  			ereport(FATAL,
  					(errmsg("could not create any TCP/IP sockets")));
  
  		list_free(elemlist);
  		pfree(rawstring);
  	}
  
  #ifdef USE_BONJOUR
  	/* Register for Bonjour only if we opened TCP socket(s) */
  	if (enable_bonjour && ListenSocket[0] != PGINVALID_SOCKET)
  	{
  		DNSServiceErrorType err;
  
  		/*
  		 * We pass 0 for interface_index, which will result in registering on
  		 * all "applicable" interfaces.  It's not entirely clear from the
  		 * DNS-SD docs whether this would be appropriate if we have bound to
  		 * just a subset of the available network interfaces.
  		 */
  		err = DNSServiceRegister(&bonjour_sdref,
  								 0,
  								 0,
  								 bonjour_name,
  								 "_postgresql._tcp.",
  								 NULL,
  								 NULL,
  								 pg_hton16(PostPortNumber),
  								 0,
  								 NULL,
  								 NULL,
  								 NULL);
  		if (err != kDNSServiceErr_NoError)
  			ereport(LOG,
  					(errmsg("DNSServiceRegister() failed: error code %ld",
  							(long) err)));
  
  		/*
  		 * We don't bother to read the mDNS daemon's reply, and we expect that
  		 * it will automatically terminate our registration when the socket is
  		 * closed at postmaster termination.  So there's nothing more to be
  		 * done here.  However, the bonjour_sdref is kept around so that
  		 * forked children can close their copies of the socket.
  		 */
  	}
  #endif
  
  #ifdef HAVE_UNIX_SOCKETS
  	if (Unix_socket_directories)
  	{
  		char	   *rawstring;
  		List	   *elemlist;
  		ListCell   *l;
  		int			success = 0;
  
  		/* Need a modifiable copy of Unix_socket_directories */
  		rawstring = pstrdup(Unix_socket_directories);
  
  		/* Parse string into list of directories */
  		if (!SplitDirectoriesString(rawstring, ',', &elemlist))
  		{
  			/* syntax error in list */
  			ereport(FATAL,
  					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  					 errmsg("invalid list syntax in parameter \"%s\"",
  							"unix_socket_directories")));
  		}
  
  		foreach(l, elemlist)
  		{
  			char	   *socketdir = (char *) lfirst(l);
  
  			status = StreamServerPort(AF_UNIX, NULL,
  									  (unsigned short) PostPortNumber,
  									  socketdir,
  									  ListenSocket, MAXLISTEN);
  
  			if (status == STATUS_OK)
  			{
  				success++;
  				/* record the first successful Unix socket in lockfile */
  				if (success == 1)
  					AddToDataDirLockFile(LOCK_FILE_LINE_SOCKET_DIR, socketdir);
  			}
  			else
  				ereport(WARNING,
  						(errmsg("could not create Unix-domain socket in directory \"%s\"",
  								socketdir)));
  		}
  
  		if (!success && elemlist != NIL)
  			ereport(FATAL,
  					(errmsg("could not create any Unix-domain sockets")));
  
  		list_free_deep(elemlist);
  		pfree(rawstring);
  	}
  #endif
  
  	/*
  	 * check that we have some socket to listen on
  	 */
  	if (ListenSocket[0] == PGINVALID_SOCKET)
  		ereport(FATAL,
  				(errmsg("no socket created for listening")));
  
  	/*
  	 * If no valid TCP ports, write an empty line for listen address,
  	 * indicating the Unix socket must be used.  Note that this line is not
  	 * added to the lock file until there is a socket backing it.
  	 */
  	if (!listen_addr_saved)
  		AddToDataDirLockFile(LOCK_FILE_LINE_LISTEN_ADDR, "");
  
  	/*
  	 * Record postmaster options.  We delay this till now to avoid recording
  	 * bogus options (eg, unusable port number).
  	 */
  	if (!CreateOptsFile(argc, argv, my_exec_path))
  		ExitPostmaster(1);
  
  	/*
  	 * Write the external PID file if requested
  	 */
  	if (external_pid_file)
  	{
  		FILE	   *fpidfile = fopen(external_pid_file, "w");
  
  		if (fpidfile)
  		{
  			fprintf(fpidfile, "%d\n", MyProcPid);
  			fclose(fpidfile);
  
  			/* Make PID file world readable */
  			if (chmod(external_pid_file, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) != 0)
  				write_stderr("%s: could not change permissions of external PID file \"%s\": %s\n",
  							 progname, external_pid_file, strerror(errno));
  		}
  		else
  			write_stderr("%s: could not write external PID file \"%s\": %s\n",
  						 progname, external_pid_file, strerror(errno));
  
  		on_proc_exit(unlink_external_pid_file, 0);
  	}
  
  	/*
  	 * Remove old temporary files.  At this point there can be no other
  	 * Postgres processes running in this directory, so this should be safe.
  	 */
  	RemovePgTempFiles();
  
  	/*
  	 * Initialize the autovacuum subsystem (again, no process start yet)
  	 */
  	autovac_init();
  
  	/*
  	 * Load configuration files for client authentication.
  	 */
  	if (!load_hba())
  	{
  		/*
  		 * It makes no sense to continue if we fail to load the HBA file,
  		 * since there is no way to connect to the database in this case.
  		 */
  		ereport(FATAL,
  				(errmsg("could not load pg_hba.conf")));
  	}
  	if (!load_ident())
  	{
  		/*
  		 * We can start up without the IDENT file, although it means that you
  		 * cannot log in using any of the authentication methods that need a
  		 * user name mapping. load_ident() already logged the details of error
  		 * to the log.
  		 */
  	}
  
  #ifdef HAVE_PTHREAD_IS_THREADED_NP
  
  	/*
  	 * On macOS, libintl replaces setlocale() with a version that calls
  	 * CFLocaleCopyCurrent() when its second argument is "" and every relevant
  	 * environment variable is unset or empty.  CFLocaleCopyCurrent() makes
  	 * the process multithreaded.  The postmaster calls sigprocmask() and
  	 * calls fork() without an immediate exec(), both of which have undefined
  	 * behavior in a multithreaded program.  A multithreaded postmaster is the
  	 * normal case on Windows, which offers neither fork() nor sigprocmask().
  	 */
  	if (pthread_is_threaded_np() != 0)
  		ereport(FATAL,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("postmaster became multithreaded during startup"),
  				 errhint("Set the LC_ALL environment variable to a valid locale.")));
  #endif
  
  	/*
  	 * Remember postmaster startup time
  	 */
  	PgStartTime = GetCurrentTimestamp();
  
  	/*
  	 * Report postmaster status in the postmaster.pid file, to allow pg_ctl to
  	 * see what's happening.
  	 */
  	AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STARTING);
  
  	/* Start bgwriter and checkpointer so they can help with recovery */
  	if (CheckpointerPID == 0)
  		CheckpointerPID = StartCheckpointer();
  	if (BgWriterPID == 0)
  		BgWriterPID = StartBackgroundWriter();
  
  	/*
  	 * We're ready to rock and roll...
  	 */
  	StartupPID = StartupDataBase();
  	Assert(StartupPID != 0);
  	StartupStatus = STARTUP_RUNNING;
  	pmState = PM_STARTUP;
  
  	/* Some workers may be scheduled to start now */
  	maybe_start_bgworkers();
  
  	status = ServerLoop();
  
  	/*
  	 * ServerLoop probably shouldn't ever return, but if it does, close down.
  	 */
  	ExitPostmaster(status != STATUS_OK);
  
  	abort();					/* not reached */
  }
  
  
  /*
   * on_proc_exit callback to close server's listen sockets
   */
  static void
  CloseServerPorts(int status, Datum arg)
  {
  	int			i;
  
  	/*
  	 * First, explicitly close all the socket FDs.  We used to just let this
  	 * happen implicitly at postmaster exit, but it's better to close them
  	 * before we remove the postmaster.pid lockfile; otherwise there's a race
  	 * condition if a new postmaster wants to re-use the TCP port number.
  	 */
  	for (i = 0; i < MAXLISTEN; i++)
  	{
  		if (ListenSocket[i] != PGINVALID_SOCKET)
  		{
  			StreamClose(ListenSocket[i]);
  			ListenSocket[i] = PGINVALID_SOCKET;
  		}
  	}
  
  	/*
  	 * Next, remove any filesystem entries for Unix sockets.  To avoid race
  	 * conditions against incoming postmasters, this must happen after closing
  	 * the sockets and before removing lock files.
  	 */
  	RemoveSocketFiles();
  
  	/*
  	 * We don't do anything about socket lock files here; those will be
  	 * removed in a later on_proc_exit callback.
  	 */
  }
  
  /*
   * on_proc_exit callback to delete external_pid_file
   */
  static void
  unlink_external_pid_file(int status, Datum arg)
  {
  	if (external_pid_file)
  		unlink(external_pid_file);
  }
  
  
  /*
   * Compute and check the directory paths to files that are part of the
   * installation (as deduced from the postgres executable's own location)
   */
  static void
  getInstallationPaths(const char *argv0)
  {
  	DIR		   *pdir;
  
  	/* Locate the postgres executable itself */
  	if (find_my_exec(argv0, my_exec_path) < 0)
  		ereport(FATAL,
  				(errmsg("%s: could not locate my own executable path", argv0)));
  
  #ifdef EXEC_BACKEND
  	/* Locate executable backend before we change working directory */
  	if (find_other_exec(argv0, "postgres", PG_BACKEND_VERSIONSTR,
  						postgres_exec_path) < 0)
  		ereport(FATAL,
  				(errmsg("%s: could not locate matching postgres executable",
  						argv0)));
  #endif
  
  	/*
  	 * Locate the pkglib directory --- this has to be set early in case we try
  	 * to load any modules from it in response to postgresql.conf entries.
  	 */
  	get_pkglib_path(my_exec_path, pkglib_path);
  
  	/*
  	 * Verify that there's a readable directory there; otherwise the Postgres
  	 * installation is incomplete or corrupt.  (A typical cause of this
  	 * failure is that the postgres executable has been moved or hardlinked to
  	 * some directory that's not a sibling of the installation lib/
  	 * directory.)
  	 */
  	pdir = AllocateDir(pkglib_path);
  	if (pdir == NULL)
  		ereport(ERROR,
  				(errcode_for_file_access(),
  				 errmsg("could not open directory \"%s\": %m",
  						pkglib_path),
  				 errhint("This may indicate an incomplete PostgreSQL installation, or that the file \"%s\" has been moved away from its proper location.",
  						 my_exec_path)));
  	FreeDir(pdir);
  
  	/*
  	 * XXX is it worth similarly checking the share/ directory?  If the lib/
  	 * directory is there, then share/ probably is too.
  	 */
  }
  
  /*
   * Check that pg_control exists in the correct location in the data directory.
   *
   * No attempt is made to validate the contents of pg_control here.  This is
   * just a sanity check to see if we are looking at a real data directory.
   */
  static void
  checkControlFile(void)
  {
  	char		path[MAXPGPATH];
  	FILE	   *fp;
  
  	snprintf(path, sizeof(path), "%s/global/pg_control", DataDir);
  
  	fp = AllocateFile(path, PG_BINARY_R);
  	if (fp == NULL)
  	{
  		write_stderr("%s: could not find the database system\n"
  					 "Expected to find it in the directory \"%s\",\n"
  					 "but could not open file \"%s\": %s\n",
  					 progname, DataDir, path, strerror(errno));
  		ExitPostmaster(2);
  	}
  	FreeFile(fp);
  }
  
  /*
   * Determine how long should we let ServerLoop sleep.
   *
   * In normal conditions we wait at most one minute, to ensure that the other
   * background tasks handled by ServerLoop get done even when no requests are
   * arriving.  However, if there are background workers waiting to be started,
   * we don't actually sleep so that they are quickly serviced.  Other exception
   * cases are as shown in the code.
   */
  static void
  DetermineSleepTime(struct timeval *timeout)
  {
  	TimestampTz next_wakeup = 0;
  
  	/*
  	 * Normal case: either there are no background workers at all, or we're in
  	 * a shutdown sequence (during which we ignore bgworkers altogether).
  	 */
  	if (Shutdown > NoShutdown ||
  		(!StartWorkerNeeded && !HaveCrashedWorker))
  	{
  		if (AbortStartTime != 0)
  		{
  			/* time left to abort; clamp to 0 in case it already expired */
  			timeout->tv_sec = SIGKILL_CHILDREN_AFTER_SECS -
  				(time(NULL) - AbortStartTime);
  			timeout->tv_sec = Max(timeout->tv_sec, 0);
  			timeout->tv_usec = 0;
  		}
  		else
  		{
  			timeout->tv_sec = 60;
  			timeout->tv_usec = 0;
  		}
  		return;
  	}
  
  	if (StartWorkerNeeded)
  	{
  		timeout->tv_sec = 0;
  		timeout->tv_usec = 0;
  		return;
  	}
  
  	if (HaveCrashedWorker)
  	{
  		slist_mutable_iter siter;
  
  		/*
  		 * When there are crashed bgworkers, we sleep just long enough that
  		 * they are restarted when they request to be.  Scan the list to
  		 * determine the minimum of all wakeup times according to most recent
  		 * crash time and requested restart interval.
  		 */
  		slist_foreach_modify(siter, &BackgroundWorkerList)
  		{
  			RegisteredBgWorker *rw;
  			TimestampTz this_wakeup;
  
  			rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
  
  			if (rw->rw_crashed_at == 0)
  				continue;
  
  			if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART
  				|| rw->rw_terminate)
  			{
  				ForgetBackgroundWorker(&siter);
  				continue;
  			}
  
  			this_wakeup = TimestampTzPlusMilliseconds(rw->rw_crashed_at,
  													  1000L * rw->rw_worker.bgw_restart_time);
  			if (next_wakeup == 0 || this_wakeup < next_wakeup)
  				next_wakeup = this_wakeup;
  		}
  	}
  
  	if (next_wakeup != 0)
  	{
  		long		secs;
  		int			microsecs;
  
  		TimestampDifference(GetCurrentTimestamp(), next_wakeup,
  							&secs, &microsecs);
  		timeout->tv_sec = secs;
  		timeout->tv_usec = microsecs;
  
  		/* Ensure we don't exceed one minute */
  		if (timeout->tv_sec > 60)
  		{
  			timeout->tv_sec = 60;
  			timeout->tv_usec = 0;
  		}
  	}
  	else
  	{
  		timeout->tv_sec = 60;
  		timeout->tv_usec = 0;
  	}
  }
  
  /*
   * Main idle loop of postmaster
   *
   * NB: Needs to be called with signals blocked
   */
  static int
  ServerLoop(void)
  {
  	fd_set		readmask;
  	int			nSockets;
  	time_t		last_lockfile_recheck_time,
  				last_touch_time;
  
  	last_lockfile_recheck_time = last_touch_time = time(NULL);
  
  	nSockets = initMasks(&readmask);
  
  	for (;;)
  	{
  		fd_set		rmask;
  		int			selres;
  		time_t		now;
  
  		/*
  		 * Wait for a connection request to arrive.
  		 *
  		 * We block all signals except while sleeping. That makes it safe for
  		 * signal handlers, which again block all signals while executing, to
  		 * do nontrivial work.
  		 *
  		 * If we are in PM_WAIT_DEAD_END state, then we don't want to accept
  		 * any new connections, so we don't call select(), and just sleep.
  		 */
  		memcpy((char *) &rmask, (char *) &readmask, sizeof(fd_set));
  
  		if (pmState == PM_WAIT_DEAD_END)
  		{
  			PG_SETMASK(&UnBlockSig);
  
  			pg_usleep(100000L); /* 100 msec seems reasonable */
  			selres = 0;
  
  			PG_SETMASK(&BlockSig);
  		}
  		else
  		{
  			/* must set timeout each time; some OSes change it! */
  			struct timeval timeout;
  
  			/* Needs to run with blocked signals! */
  			DetermineSleepTime(&timeout);
  
  			PG_SETMASK(&UnBlockSig);
  
  			selres = select(nSockets, &rmask, NULL, NULL, &timeout);
  
  			PG_SETMASK(&BlockSig);
  		}
  
  		/* Now check the select() result */
  		if (selres < 0)
  		{
  			if (errno != EINTR && errno != EWOULDBLOCK)
  			{
  				ereport(LOG,
  						(errcode_for_socket_access(),
  						 errmsg("select() failed in postmaster: %m")));
  				return STATUS_ERROR;
  			}
  		}
  
  		/*
  		 * New connection pending on any of our sockets? If so, fork a child
  		 * process to deal with it.
  		 */
  		if (selres > 0)
  		{
  			int			i;
  
  			for (i = 0; i < MAXLISTEN; i++)
  			{
  				if (ListenSocket[i] == PGINVALID_SOCKET)
  					break;
  				if (FD_ISSET(ListenSocket[i], &rmask))
  				{
  					Port	   *port;
  
  					port = ConnCreate(ListenSocket[i]);
  					if (port)
  					{
  						BackendStartup(port);
  
  						/*
  						 * We no longer need the open socket or port structure
  						 * in this process
  						 */
  						StreamClose(port->sock);
  						ConnFree(port);
  					}
  				}
  			}
  		}
  
  		/* If we have lost the log collector, try to start a new one */
  		if (SysLoggerPID == 0 && Logging_collector)
  			SysLoggerPID = SysLogger_Start();
  
  		/*
  		 * If no background writer process is running, and we are not in a
  		 * state that prevents it, start one.  It doesn't matter if this
  		 * fails, we'll just try again later.  Likewise for the checkpointer.
  		 */
  		if (pmState == PM_RUN || pmState == PM_RECOVERY ||
  			pmState == PM_HOT_STANDBY || pmState == PM_STARTUP)
  		{
  			if (CheckpointerPID == 0)
  				CheckpointerPID = StartCheckpointer();
  			if (BgWriterPID == 0)
  				BgWriterPID = StartBackgroundWriter();
  		}
  
  		/*
  		 * Likewise, if we have lost the walwriter process, try to start a new
  		 * one.  But this is needed only in normal operation (else we cannot
  		 * be writing any new WAL).
  		 */
  		if (WalWriterPID == 0 && pmState == PM_RUN)
  			WalWriterPID = StartWalWriter();
  
  		/*
  		 * If we have lost the autovacuum launcher, try to start a new one. We
  		 * don't want autovacuum to run in binary upgrade mode because
  		 * autovacuum might update relfrozenxid for empty tables before the
  		 * physical files are put in place.
  		 */
  		if (!IsBinaryUpgrade && AutoVacPID == 0 &&
  			(AutoVacuumingActive() || start_autovac_launcher) &&
  			pmState == PM_RUN)
  		{
  			AutoVacPID = StartAutoVacLauncher();
  			if (AutoVacPID != 0)
  				start_autovac_launcher = false; /* signal processed */
  		}
  
  		/* If we have lost the archiver, try to start a new one. */
  		if (PgArchPID == 0 && PgArchStartupAllowed())
  			PgArchPID = StartArchiver();
  
  		/* If we need to signal the autovacuum launcher, do so now */
  		if (avlauncher_needs_signal)
  		{
  			avlauncher_needs_signal = false;
  			if (AutoVacPID != 0)
  				kill(AutoVacPID, SIGUSR2);
  		}
  
  		/* If we need to start a WAL receiver, try to do that now */
  		if (WalReceiverRequested)
  			MaybeStartWalReceiver();
  
  		/* Get other worker processes running, if needed */
  		if (StartWorkerNeeded || HaveCrashedWorker)
  			maybe_start_bgworkers();
  
  #ifdef HAVE_PTHREAD_IS_THREADED_NP
  
  		/*
  		 * With assertions enabled, check regularly for appearance of
  		 * additional threads.  All builds check at start and exit.
  		 */
  		Assert(pthread_is_threaded_np() == 0);
  #endif
  
  		/*
  		 * Lastly, check to see if it's time to do some things that we don't
  		 * want to do every single time through the loop, because they're a
  		 * bit expensive.  Note that there's up to a minute of slop in when
  		 * these tasks will be performed, since DetermineSleepTime() will let
  		 * us sleep at most that long; except for SIGKILL timeout which has
  		 * special-case logic there.
  		 */
  		now = time(NULL);
  
  		/*
  		 * If we already sent SIGQUIT to children and they are slow to shut
  		 * down, it's time to send them SIGKILL.  This doesn't happen
  		 * normally, but under certain conditions backends can get stuck while
  		 * shutting down.  This is a last measure to get them unwedged.
  		 *
  		 * Note we also do this during recovery from a process crash.
  		 */
  		if ((Shutdown >= ImmediateShutdown || (FatalError && !SendStop)) &&
  			AbortStartTime != 0 &&
  			(now - AbortStartTime) >= SIGKILL_CHILDREN_AFTER_SECS)
  		{
  			/* We were gentle with them before. Not anymore */
  			ereport(LOG,
  					(errmsg("issuing SIGKILL to recalcitrant children")));
  			TerminateChildren(SIGKILL);
  			/* reset flag so we don't SIGKILL again */
  			AbortStartTime = 0;
  		}
  
  		/*
  		 * Once a minute, verify that postmaster.pid hasn't been removed or
  		 * overwritten.  If it has, we force a shutdown.  This avoids having
  		 * postmasters and child processes hanging around after their database
  		 * is gone, and maybe causing problems if a new database cluster is
  		 * created in the same place.  It also provides some protection
  		 * against a DBA foolishly removing postmaster.pid and manually
  		 * starting a new postmaster.  Data corruption is likely to ensue from
  		 * that anyway, but we can minimize the damage by aborting ASAP.
  		 */
  		if (now - last_lockfile_recheck_time >= 1 * SECS_PER_MINUTE)
  		{
  			if (!RecheckDataDirLockFile())
  			{
  				ereport(LOG,
  						(errmsg("performing immediate shutdown because data directory lock file is invalid")));
  				kill(MyProcPid, SIGQUIT);
  			}
  			last_lockfile_recheck_time = now;
  		}
  
  		/*
  		 * Touch Unix socket and lock files every 58 minutes, to ensure that
  		 * they are not removed by overzealous /tmp-cleaning tasks.  We assume
  		 * no one runs cleaners with cutoff times of less than an hour ...
  		 */
  		if (now - last_touch_time >= 58 * SECS_PER_MINUTE)
  		{
  			TouchSocketFiles();
  			TouchSocketLockFiles();
  			last_touch_time = now;
  		}
  	}
  }
  
  /*
   * Initialise the masks for select() for the ports we are listening on.
   * Return the number of sockets to listen on.
   */
  static int
  initMasks(fd_set *rmask)
  {
  	int			maxsock = -1;
  	int			i;
  
  	FD_ZERO(rmask);
  
  	for (i = 0; i < MAXLISTEN; i++)
  	{
  		int			fd = ListenSocket[i];
  
  		if (fd == PGINVALID_SOCKET)
  			break;
  		FD_SET(fd, rmask);
  
  		if (fd > maxsock)
  			maxsock = fd;
  	}
  
  	return maxsock + 1;
  }
  
  
  /*
   * Read a client's startup packet and do something according to it.
   *
   * Returns STATUS_OK or STATUS_ERROR, or might call ereport(FATAL) and
   * not return at all.
   *
   * (Note that ereport(FATAL) stuff is sent to the client, so only use it
   * if that's what you want.  Return STATUS_ERROR if you don't want to
   * send anything to the client, which would typically be appropriate
   * if we detect a communications failure.)
   *
   * Set ssl_done and/or gss_done when negotiation of an encrypted layer
   * (currently, TLS or GSSAPI) is completed. A successful negotiation of either
   * encryption layer sets both flags, but a rejected negotiation sets only the
   * flag for that layer, since the client may wish to try the other one. We
   * should make no assumption here about the order in which the client may make
   * requests.
   */
  static int
  ProcessStartupPacket(Port *port, bool ssl_done, bool gss_done)
  {
  	int32		len;
  	char	   *buf;
  	ProtocolVersion proto;
  	MemoryContext oldcontext;
  
  	pq_startmsgread();
  
  	/*
  	 * Grab the first byte of the length word separately, so that we can tell
  	 * whether we have no data at all or an incomplete packet.  (This might
  	 * sound inefficient, but it's not really, because of buffering in
  	 * pqcomm.c.)
  	 */
  	if (pq_getbytes((char *) &len, 1) == EOF)
  	{
  		/*
  		 * If we get no data at all, don't clutter the log with a complaint;
  		 * such cases often occur for legitimate reasons.  An example is that
  		 * we might be here after responding to NEGOTIATE_SSL_CODE, and if the
  		 * client didn't like our response, it'll probably just drop the
  		 * connection.  Service-monitoring software also often just opens and
  		 * closes a connection without sending anything.  (So do port
  		 * scanners, which may be less benign, but it's not really our job to
  		 * notice those.)
  		 */
  		return STATUS_ERROR;
  	}
  
  	if (pq_getbytes(((char *) &len) + 1, 3) == EOF)
  	{
  		/* Got a partial length word, so bleat about that */
  		if (!ssl_done && !gss_done)
  			ereport(COMMERROR,
  					(errcode(ERRCODE_PROTOCOL_VIOLATION),
  					 errmsg("incomplete startup packet")));
  		return STATUS_ERROR;
  	}
  
  	len = pg_ntoh32(len);
  	len -= 4;
  
  	if (len < (int32) sizeof(ProtocolVersion) ||
  		len > MAX_STARTUP_PACKET_LENGTH)
  	{
  		ereport(COMMERROR,
  				(errcode(ERRCODE_PROTOCOL_VIOLATION),
  				 errmsg("invalid length of startup packet")));
  		return STATUS_ERROR;
  	}
  
  	/*
  	 * Allocate space to hold the startup packet, plus one extra byte that's
  	 * initialized to be zero.  This ensures we will have null termination of
  	 * all strings inside the packet.
  	 */
  	buf = palloc(len + 1);
  	buf[len] = '\0';
  
  	if (pq_getbytes(buf, len) == EOF)
  	{
  		ereport(COMMERROR,
  				(errcode(ERRCODE_PROTOCOL_VIOLATION),
  				 errmsg("incomplete startup packet")));
  		return STATUS_ERROR;
  	}
  	pq_endmsgread();
  
  	/*
  	 * The first field is either a protocol version number or a special
  	 * request code.
  	 */
  	port->proto = proto = pg_ntoh32(*((ProtocolVersion *) buf));
  
  	if (proto == CANCEL_REQUEST_CODE)
  	{
  		processCancelRequest(port, buf);
  		/* Not really an error, but we don't want to proceed further */
  		return STATUS_ERROR;
  	}
  
  	if (proto == NEGOTIATE_SSL_CODE && !ssl_done)
  	{
  		char		SSLok;
  
  #ifdef USE_SSL
  		/* No SSL when disabled or on Unix sockets */
  		if (!LoadedSSL || port->laddr.addr.ss_family == AF_UNIX)
  			SSLok = 'N';
  		else
  			SSLok = 'S';		/* Support for SSL */
  #else
  		SSLok = 'N';			/* No support for SSL */
  #endif
  
  retry1:
  		if (send(port->sock, &SSLok, 1, 0) != 1)
  		{
  			if (errno == EINTR)
  				goto retry1;	/* if interrupted, just retry */
  			ereport(COMMERROR,
  					(errcode_for_socket_access(),
  					 errmsg("failed to send SSL negotiation response: %m")));
  			return STATUS_ERROR;	/* close the connection */
  		}
  
  #ifdef USE_SSL
  		if (SSLok == 'S' && secure_open_server(port) == -1)
  			return STATUS_ERROR;
  #endif
  
  		/*
  		 * At this point we should have no data already buffered.  If we do,
  		 * it was received before we performed the SSL handshake, so it wasn't
  		 * encrypted and indeed may have been injected by a man-in-the-middle.
  		 * We report this case to the client.
  		 */
  		if (pq_buffer_has_data())
  			ereport(FATAL,
  					(errcode(ERRCODE_PROTOCOL_VIOLATION),
  					 errmsg("received unencrypted data after SSL request"),
  					 errdetail("This could be either a client-software bug or evidence of an attempted man-in-the-middle attack.")));
  
  		/*
  		 * regular startup packet, cancel, etc packet should follow, but not
  		 * another SSL negotiation request, and a GSS request should only
  		 * follow if SSL was rejected (client may negotiate in either order)
  		 */
  		return ProcessStartupPacket(port, true, SSLok == 'S');
  	}
  	else if (proto == NEGOTIATE_GSS_CODE && !gss_done)
  	{
  		char		GSSok = 'N';
  
  #ifdef ENABLE_GSS
  		/* No GSSAPI encryption when on Unix socket */
  		if (port->laddr.addr.ss_family != AF_UNIX)
  			GSSok = 'G';
  #endif
  
  		while (send(port->sock, &GSSok, 1, 0) != 1)
  		{
  			if (errno == EINTR)
  				continue;
  			ereport(COMMERROR,
  					(errcode_for_socket_access(),
  					 errmsg("failed to send GSSAPI negotiation response: %m")));
  			return STATUS_ERROR;	/* close the connection */
  		}
  
  #ifdef ENABLE_GSS
  		if (GSSok == 'G' && secure_open_gssapi(port) == -1)
  			return STATUS_ERROR;
  #endif
  
  		/*
  		 * At this point we should have no data already buffered.  If we do,
  		 * it was received before we performed the GSS handshake, so it wasn't
  		 * encrypted and indeed may have been injected by a man-in-the-middle.
  		 * We report this case to the client.
  		 */
  		if (pq_buffer_has_data())
  			ereport(FATAL,
  					(errcode(ERRCODE_PROTOCOL_VIOLATION),
  					 errmsg("received unencrypted data after GSSAPI encryption request"),
  					 errdetail("This could be either a client-software bug or evidence of an attempted man-in-the-middle attack.")));
  
  		/*
  		 * regular startup packet, cancel, etc packet should follow, but not
  		 * another GSS negotiation request, and an SSL request should only
  		 * follow if GSS was rejected (client may negotiate in either order)
  		 */
  		return ProcessStartupPacket(port, GSSok == 'G', true);
  	}
  
  	/* Could add additional special packet types here */
  
  	/*
  	 * Set FrontendProtocol now so that ereport() knows what format to send if
  	 * we fail during startup.
  	 */
  	FrontendProtocol = proto;
  
  	/* Check that the major protocol version is in range. */
  	if (PG_PROTOCOL_MAJOR(proto) < PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST) ||
  		PG_PROTOCOL_MAJOR(proto) > PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST))
  		ereport(FATAL,
  				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  				 errmsg("unsupported frontend protocol %u.%u: server supports %u.0 to %u.%u",
  						PG_PROTOCOL_MAJOR(proto), PG_PROTOCOL_MINOR(proto),
  						PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST),
  						PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST),
  						PG_PROTOCOL_MINOR(PG_PROTOCOL_LATEST))));
  
  	/*
  	 * Now fetch parameters out of startup packet and save them into the Port
  	 * structure.  All data structures attached to the Port struct must be
  	 * allocated in TopMemoryContext so that they will remain available in a
  	 * running backend (even after PostmasterContext is destroyed).  We need
  	 * not worry about leaking this storage on failure, since we aren't in the
  	 * postmaster process anymore.
  	 */
  	oldcontext = MemoryContextSwitchTo(TopMemoryContext);
  
  	/* Handle protocol version 3 startup packet */
  	{
  		int32		offset = sizeof(ProtocolVersion);
  		List	   *unrecognized_protocol_options = NIL;
  
  		/*
  		 * Scan packet body for name/option pairs.  We can assume any string
  		 * beginning within the packet body is null-terminated, thanks to
  		 * zeroing extra byte above.
  		 */
  		port->guc_options = NIL;
  
  		while (offset < len)
  		{
  			char	   *nameptr = buf + offset;
  			int32		valoffset;
  			char	   *valptr;
  
  			if (*nameptr == '\0')
  				break;			/* found packet terminator */
  			valoffset = offset + strlen(nameptr) + 1;
  			if (valoffset >= len)
  				break;			/* missing value, will complain below */
  			valptr = buf + valoffset;
  
  			if (strcmp(nameptr, "database") == 0)
  				port->database_name = pstrdup(valptr);
  			else if (strcmp(nameptr, "user") == 0)
  				port->user_name = pstrdup(valptr);
  			else if (strcmp(nameptr, "options") == 0)
  				port->cmdline_options = pstrdup(valptr);
  			else if (strcmp(nameptr, "replication") == 0)
  			{
  				/*
  				 * Due to backward compatibility concerns the replication
  				 * parameter is a hybrid beast which allows the value to be
  				 * either boolean or the string 'database'. The latter
  				 * connects to a specific database which is e.g. required for
  				 * logical decoding while.
  				 */
  				if (strcmp(valptr, "database") == 0)
  				{
  					am_walsender = true;
  					am_db_walsender = true;
  				}
  				else if (!parse_bool(valptr, &am_walsender))
  					ereport(FATAL,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("invalid value for parameter \"%s\": \"%s\"",
  									"replication",
  									valptr),
  							 errhint("Valid values are: \"false\", 0, \"true\", 1, \"database\".")));
  			}
  			else if (strncmp(nameptr, "_pq_.", 5) == 0)
  			{
  				/*
  				 * Any option beginning with _pq_. is reserved for use as a
  				 * protocol-level option, but at present no such options are
  				 * defined.
  				 */
  				unrecognized_protocol_options =
  					lappend(unrecognized_protocol_options, pstrdup(nameptr));
  			}
  			else
  			{
  				/* Assume it's a generic GUC option */
  				port->guc_options = lappend(port->guc_options,
  											pstrdup(nameptr));
  				port->guc_options = lappend(port->guc_options,
  											pstrdup(valptr));
  
  				/*
  				 * Copy application_name to port if we come across it.  This
  				 * is done so we can log the application_name in the
  				 * connection authorization message.  Note that the GUC would
  				 * be used but we haven't gone through GUC setup yet.
  				 */
  				if (strcmp(nameptr, "application_name") == 0)
  				{
  					char	   *tmp_app_name = pstrdup(valptr);
  
  					pg_clean_ascii(tmp_app_name);
  
  					port->application_name = tmp_app_name;
  				}
  			}
  			offset = valoffset + strlen(valptr) + 1;
  		}
  
  		/*
  		 * If we didn't find a packet terminator exactly at the end of the
  		 * given packet length, complain.
  		 */
  		if (offset != len - 1)
  			ereport(FATAL,
  					(errcode(ERRCODE_PROTOCOL_VIOLATION),
  					 errmsg("invalid startup packet layout: expected terminator as last byte")));
  
  		/*
  		 * If the client requested a newer protocol version or if the client
  		 * requested any protocol options we didn't recognize, let them know
  		 * the newest minor protocol version we do support and the names of
  		 * any unrecognized options.
  		 */
  		if (PG_PROTOCOL_MINOR(proto) > PG_PROTOCOL_MINOR(PG_PROTOCOL_LATEST) ||
  			unrecognized_protocol_options != NIL)
  			SendNegotiateProtocolVersion(unrecognized_protocol_options);
  	}
  
  	/* Check a user name was given. */
  	if (port->user_name == NULL || port->user_name[0] == '\0')
  		ereport(FATAL,
  				(errcode(ERRCODE_INVALID_AUTHORIZATION_SPECIFICATION),
  				 errmsg("no PostgreSQL user name specified in startup packet")));
  
  	/* The database defaults to the user name. */
  	if (port->database_name == NULL || port->database_name[0] == '\0')
  		port->database_name = pstrdup(port->user_name);
  
  	if (Db_user_namespace)
  	{
  		/*
  		 * If user@, it is a global user, remove '@'. We only want to do this
  		 * if there is an '@' at the end and no earlier in the user string or
  		 * they may fake as a local user of another database attaching to this
  		 * database.
  		 */
  		if (strchr(port->user_name, '@') ==
  			port->user_name + strlen(port->user_name) - 1)
  			*strchr(port->user_name, '@') = '\0';
  		else
  		{
  			/* Append '@' and dbname */
  			port->user_name = psprintf("%s@%s", port->user_name, port->database_name);
  		}
  	}
  
  	/*
  	 * Truncate given database and user names to length of a Postgres name.
  	 * This avoids lookup failures when overlength names are given.
  	 */
  	if (strlen(port->database_name) >= NAMEDATALEN)
  		port->database_name[NAMEDATALEN - 1] = '\0';
  	if (strlen(port->user_name) >= NAMEDATALEN)
  		port->user_name[NAMEDATALEN - 1] = '\0';
  
  	if (am_walsender)
  		MyBackendType = B_WAL_SENDER;
  	else
  		MyBackendType = B_BACKEND;
  
  	/*
  	 * Normal walsender backends, e.g. for streaming replication, are not
  	 * connected to a particular database. But walsenders used for logical
  	 * replication need to connect to a specific database. We allow streaming
  	 * replication commands to be issued even if connected to a database as it
  	 * can make sense to first make a basebackup and then stream changes
  	 * starting from that.
  	 */
  	if (am_walsender && !am_db_walsender)
  		port->database_name[0] = '\0';
  
  	/*
  	 * Done putting stuff in TopMemoryContext.
  	 */
  	MemoryContextSwitchTo(oldcontext);
  
  	/*
  	 * If we're going to reject the connection due to database state, say so
  	 * now instead of wasting cycles on an authentication exchange. (This also
  	 * allows a pg_ping utility to be written.)
  	 */
  	switch (port->canAcceptConnections)
  	{
  		case CAC_STARTUP:
  			ereport(FATAL,
  					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
  					 errmsg("the database system is starting up")));
  			break;
  		case CAC_NOTCONSISTENT:
  			if (EnableHotStandby)
  				ereport(FATAL,
  						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
  						 errmsg("the database system is not yet accepting connections"),
  						 errdetail("Consistent recovery state has not been yet reached.")));
  			else
  				ereport(FATAL,
  						(errcode(ERRCODE_CANNOT_CONNECT_NOW),
  						 errmsg("the database system is not accepting connections"),
  						 errdetail("Hot standby mode is disabled.")));
  			break;
  		case CAC_SHUTDOWN:
  			ereport(FATAL,
  					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
  					 errmsg("the database system is shutting down")));
  			break;
  		case CAC_RECOVERY:
  			ereport(FATAL,
  					(errcode(ERRCODE_CANNOT_CONNECT_NOW),
  					 errmsg("the database system is in recovery mode")));
  			break;
  		case CAC_TOOMANY:
  			ereport(FATAL,
  					(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
  					 errmsg("sorry, too many clients already")));
  			break;
  		case CAC_OK:
  			break;
  	}
  
  	return STATUS_OK;
  }
  
  /*
   * Send a NegotiateProtocolVersion to the client.  This lets the client know
   * that they have requested a newer minor protocol version than we are able
   * to speak.  We'll speak the highest version we know about; the client can,
   * of course, abandon the connection if that's a problem.
   *
   * We also include in the response a list of protocol options we didn't
   * understand.  This allows clients to include optional parameters that might
   * be present either in newer protocol versions or third-party protocol
   * extensions without fear of having to reconnect if those options are not
   * understood, while at the same time making certain that the client is aware
   * of which options were actually accepted.
   */
  static void
  SendNegotiateProtocolVersion(List *unrecognized_protocol_options)
  {
  	StringInfoData buf;
  	ListCell   *lc;
  
  	pq_beginmessage(&buf, 'v'); /* NegotiateProtocolVersion */
  	pq_sendint32(&buf, PG_PROTOCOL_LATEST);
  	pq_sendint32(&buf, list_length(unrecognized_protocol_options));
  	foreach(lc, unrecognized_protocol_options)
  		pq_sendstring(&buf, lfirst(lc));
  	pq_endmessage(&buf);
  
  	/* no need to flush, some other message will follow */
  }
  
  /*
   * The client has sent a cancel request packet, not a normal
   * start-a-new-connection packet.  Perform the necessary processing.
   * Nothing is sent back to the client.
   */
  static void
  processCancelRequest(Port *port, void *pkt)
  {
  	CancelRequestPacket *canc = (CancelRequestPacket *) pkt;
  	int			backendPID;
  	int32		cancelAuthCode;
  	Backend    *bp;
  
  #ifndef EXEC_BACKEND
  	dlist_iter	iter;
  #else
  	int			i;
  #endif
  
  	backendPID = (int) pg_ntoh32(canc->backendPID);
  	cancelAuthCode = (int32) pg_ntoh32(canc->cancelAuthCode);
  
  	/*
  	 * See if we have a matching backend.  In the EXEC_BACKEND case, we can no
  	 * longer access the postmaster's own backend list, and must rely on the
  	 * duplicate array in shared memory.
  	 */
  #ifndef EXEC_BACKEND
  	dlist_foreach(iter, &BackendList)
  	{
  		bp = dlist_container(Backend, elem, iter.cur);
  #else
  	for (i = MaxLivePostmasterChildren() - 1; i >= 0; i--)
  	{
  		bp = (Backend *) &ShmemBackendArray[i];
  #endif
  		if (bp->pid == backendPID)
  		{
  			if (bp->cancel_key == cancelAuthCode)
  			{
  				/* Found a match; signal that backend to cancel current op */
  				ereport(DEBUG2,
  						(errmsg_internal("processing cancel request: sending SIGINT to process %d",
  										 backendPID)));
  				signal_child(bp->pid, SIGINT);
  			}
  			else
  				/* Right PID, wrong key: no way, Jose */
  				ereport(LOG,
  						(errmsg("wrong key in cancel request for process %d",
  								backendPID)));
  			return;
  		}
  #ifndef EXEC_BACKEND			/* make GNU Emacs 26.1 see brace balance */
  	}
  #else
  	}
  #endif
  
  	/* No matching backend */
  	ereport(LOG,
  			(errmsg("PID %d in cancel request did not match any process",
  					backendPID)));
  }
  
  /*
   * canAcceptConnections --- check to see if database state allows connections
   * of the specified type.  backend_type can be BACKEND_TYPE_NORMAL,
   * BACKEND_TYPE_AUTOVAC, or BACKEND_TYPE_BGWORKER.  (Note that we don't yet
   * know whether a NORMAL connection might turn into a walsender.)
   */
  static CAC_state
  canAcceptConnections(int backend_type)
  {
  	CAC_state	result = CAC_OK;
  
  	/*
  	 * Can't start backends when in startup/shutdown/inconsistent recovery
  	 * state.  We treat autovac workers the same as user backends for this
  	 * purpose.  However, bgworkers are excluded from this test; we expect
  	 * bgworker_should_start_now() decided whether the DB state allows them.
  	 */
  	if (pmState != PM_RUN && pmState != PM_HOT_STANDBY &&
  		backend_type != BACKEND_TYPE_BGWORKER)
  	{
  		if (Shutdown > NoShutdown)
  			return CAC_SHUTDOWN;	/* shutdown is pending */
  		else if (!FatalError && pmState == PM_STARTUP)
  			return CAC_STARTUP; /* normal startup */
  		else if (!FatalError && pmState == PM_RECOVERY)
  			return CAC_NOTCONSISTENT;	/* not yet at consistent recovery
  										 * state */
  		else
  			return CAC_RECOVERY;	/* else must be crash recovery */
  	}
  
  	/*
  	 * "Smart shutdown" restrictions are applied only to normal connections,
  	 * not to autovac workers or bgworkers.
  	 */
  	if (!connsAllowed && backend_type == BACKEND_TYPE_NORMAL)
  		return CAC_SHUTDOWN;	/* shutdown is pending */
  
  	/*
  	 * Don't start too many children.
  	 *
  	 * We allow more connections here than we can have backends because some
  	 * might still be authenticating; they might fail auth, or some existing
  	 * backend might exit before the auth cycle is completed.  The exact
  	 * MaxBackends limit is enforced when a new backend tries to join the
  	 * shared-inval backend array.
  	 *
  	 * The limit here must match the sizes of the per-child-process arrays;
  	 * see comments for MaxLivePostmasterChildren().
  	 */
  	if (CountChildren(BACKEND_TYPE_ALL) >= MaxLivePostmasterChildren())
  		result = CAC_TOOMANY;
  
  	return result;
  }
  
  
  /*
   * ConnCreate -- create a local connection data structure
   *
   * Returns NULL on failure, other than out-of-memory which is fatal.
   */
  static Port *
  ConnCreate(int serverFd)
  {
  	Port	   *port;
  
  	if (!(port = (Port *) calloc(1, sizeof(Port))))
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  		ExitPostmaster(1);
  	}
  
  	if (StreamConnection(serverFd, port) != STATUS_OK)
  	{
  		if (port->sock != PGINVALID_SOCKET)
  			StreamClose(port->sock);
  		ConnFree(port);
  		return NULL;
  	}
  
  	return port;
  }
  
  
  /*
   * ConnFree -- free a local connection data structure
   *
   * Caller has already closed the socket if any, so there's not much
   * to do here.
   */
  static void
  ConnFree(Port *conn)
  {
  	free(conn);
  }
  
  
  /*
   * ClosePostmasterPorts -- close all the postmaster's open sockets
   *
   * This is called during child process startup to release file descriptors
   * that are not needed by that child process.  The postmaster still has
   * them open, of course.
   *
   * Note: we pass am_syslogger as a boolean because we don't want to set
   * the global variable yet when this is called.
   */
  void
  ClosePostmasterPorts(bool am_syslogger)
  {
  	int			i;
  
  #ifndef WIN32
  
  	/*
  	 * Close the write end of postmaster death watch pipe. It's important to
  	 * do this as early as possible, so that if postmaster dies, others won't
  	 * think that it's still running because we're holding the pipe open.
  	 */
  	if (close(postmaster_alive_fds[POSTMASTER_FD_OWN]) != 0)
  		ereport(FATAL,
  				(errcode_for_file_access(),
  				 errmsg_internal("could not close postmaster death monitoring pipe in child process: %m")));
  	postmaster_alive_fds[POSTMASTER_FD_OWN] = -1;
  	/* Notify fd.c that we released one pipe FD. */
  	ReleaseExternalFD();
  #endif
  
  	/*
  	 * Close the postmaster's listen sockets.  These aren't tracked by fd.c,
  	 * so we don't call ReleaseExternalFD() here.
  	 */
  	for (i = 0; i < MAXLISTEN; i++)
  	{
  		if (ListenSocket[i] != PGINVALID_SOCKET)
  		{
  			StreamClose(ListenSocket[i]);
  			ListenSocket[i] = PGINVALID_SOCKET;
  		}
  	}
  
  	/*
  	 * If using syslogger, close the read side of the pipe.  We don't bother
  	 * tracking this in fd.c, either.
  	 */
  	if (!am_syslogger)
  	{
  #ifndef WIN32
  		if (syslogPipe[0] >= 0)
  			close(syslogPipe[0]);
  		syslogPipe[0] = -1;
  #else
  		if (syslogPipe[0])
  			CloseHandle(syslogPipe[0]);
  		syslogPipe[0] = 0;
  #endif
  	}
  
  #ifdef USE_BONJOUR
  	/* If using Bonjour, close the connection to the mDNS daemon */
  	if (bonjour_sdref)
  		close(DNSServiceRefSockFD(bonjour_sdref));
  #endif
  }
  
  
  /*
   * InitProcessGlobals -- set MyProcPid, MyStartTime[stamp], random seeds
   *
   * Called early in the postmaster and every backend.
   */
  void
  InitProcessGlobals(void)
  {
  	MyProcPid = getpid();
  	MyStartTimestamp = GetCurrentTimestamp();
  	MyStartTime = timestamptz_to_time_t(MyStartTimestamp);
  
  	/*
  	 * Set a different global seed in every process.  We want something
  	 * unpredictable, so if possible, use high-quality random bits for the
  	 * seed.  Otherwise, fall back to a seed based on timestamp and PID.
  	 */
  	if (unlikely(!pg_prng_strong_seed(&pg_global_prng_state)))
  	{
  		uint64		rseed;
  
  		/*
  		 * Since PIDs and timestamps tend to change more frequently in their
  		 * least significant bits, shift the timestamp left to allow a larger
  		 * total number of seeds in a given time period.  Since that would
  		 * leave only 20 bits of the timestamp that cycle every ~1 second,
  		 * also mix in some higher bits.
  		 */
  		rseed = ((uint64) MyProcPid) ^
  			((uint64) MyStartTimestamp << 12) ^
  			((uint64) MyStartTimestamp >> 20);
  
  		pg_prng_seed(&pg_global_prng_state, rseed);
  	}
  
  	/*
  	 * Also make sure that we've set a good seed for random(3).  Use of that
  	 * is deprecated in core Postgres, but extensions might use it.
  	 */
  #ifndef WIN32
  	srandom(pg_prng_uint32(&pg_global_prng_state));
  #endif
  }
  
  
  /*
   * reset_shared -- reset shared memory and semaphores
   */
  static void
  reset_shared(void)
  {
  	/*
  	 * Create or re-create shared memory and semaphores.
  	 *
  	 * Note: in each "cycle of life" we will normally assign the same IPC keys
  	 * (if using SysV shmem and/or semas).  This helps ensure that we will
  	 * clean up dead IPC objects if the postmaster crashes and is restarted.
  	 */
  	CreateSharedMemoryAndSemaphores();
  }
  
  
  /*
   * SIGHUP -- reread config files, and tell children to do same
   */
  static void
  SIGHUP_handler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	/*
  	 * We rely on the signal mechanism to have blocked all signals ... except
  	 * on Windows, which lacks sigaction(), so we have to do it manually.
  	 */
  #ifdef WIN32
  	PG_SETMASK(&BlockSig);
  #endif
  
  	if (Shutdown <= SmartShutdown)
  	{
  		ereport(LOG,
  				(errmsg("received SIGHUP, reloading configuration files")));
  		ProcessConfigFile(PGC_SIGHUP);
  		SignalChildren(SIGHUP);
  		if (StartupPID != 0)
  			signal_child(StartupPID, SIGHUP);
  		if (BgWriterPID != 0)
  			signal_child(BgWriterPID, SIGHUP);
  		if (CheckpointerPID != 0)
  			signal_child(CheckpointerPID, SIGHUP);
  		if (WalWriterPID != 0)
  			signal_child(WalWriterPID, SIGHUP);
  		if (WalReceiverPID != 0)
  			signal_child(WalReceiverPID, SIGHUP);
  		if (AutoVacPID != 0)
  			signal_child(AutoVacPID, SIGHUP);
  		if (PgArchPID != 0)
  			signal_child(PgArchPID, SIGHUP);
  		if (SysLoggerPID != 0)
  			signal_child(SysLoggerPID, SIGHUP);
  
  		/* Reload authentication config files too */
  		if (!load_hba())
  			ereport(LOG,
  			/* translator: %s is a configuration file */
  					(errmsg("%s was not reloaded", "pg_hba.conf")));
  
  		if (!load_ident())
  			ereport(LOG,
  					(errmsg("%s was not reloaded", "pg_ident.conf")));
  
  #ifdef USE_SSL
  		/* Reload SSL configuration as well */
  		if (EnableSSL)
  		{
  			if (secure_initialize(false) == 0)
  				LoadedSSL = true;
  			else
  				ereport(LOG,
  						(errmsg("SSL configuration was not reloaded")));
  		}
  		else
  		{
  			secure_destroy();
  			LoadedSSL = false;
  		}
  #endif
  
  #ifdef EXEC_BACKEND
  		/* Update the starting-point file for future children */
  		write_nondefault_variables(PGC_SIGHUP);
  #endif
  	}
  
  #ifdef WIN32
  	PG_SETMASK(&UnBlockSig);
  #endif
  
  	errno = save_errno;
  }
  
  
  /*
   * pmdie -- signal handler for processing various postmaster signals.
   */
  static void
  pmdie(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	/*
  	 * We rely on the signal mechanism to have blocked all signals ... except
  	 * on Windows, which lacks sigaction(), so we have to do it manually.
  	 */
  #ifdef WIN32
  	PG_SETMASK(&BlockSig);
  #endif
  
  	ereport(DEBUG2,
  			(errmsg_internal("postmaster received signal %d",
  							 postgres_signal_arg)));
  
  	switch (postgres_signal_arg)
  	{
  		case SIGTERM:
  
  			/*
  			 * Smart Shutdown:
  			 *
  			 * Wait for children to end their work, then shut down.
  			 */
  			if (Shutdown >= SmartShutdown)
  				break;
  			Shutdown = SmartShutdown;
  			ereport(LOG,
  					(errmsg("received smart shutdown request")));
  
  			/* Report status */
  			AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
  #ifdef USE_SYSTEMD
  			sd_notify(0, "STOPPING=1");
  #endif
  
  			/*
  			 * If we reached normal running, we go straight to waiting for
  			 * client backends to exit.  If already in PM_STOP_BACKENDS or
  			 * a later state, do not change it.
  			 */
  			if (pmState == PM_RUN || pmState == PM_HOT_STANDBY)
  				connsAllowed = false;
  			else if (pmState == PM_STARTUP || pmState == PM_RECOVERY)
  			{
  				/* There should be no clients, so proceed to stop children */
  				pmState = PM_STOP_BACKENDS;
  			}
  
  			/*
  			 * Now wait for online backup mode to end and backends to exit. If
  			 * that is already the case, PostmasterStateMachine will take the
  			 * next step.
  			 */
  			PostmasterStateMachine();
  			break;
  
  		case SIGINT:
  
  			/*
  			 * Fast Shutdown:
  			 *
  			 * Abort all children with SIGTERM (rollback active transactions
  			 * and exit) and shut down when they are gone.
  			 */
  			if (Shutdown >= FastShutdown)
  				break;
  			Shutdown = FastShutdown;
  			ereport(LOG,
  					(errmsg("received fast shutdown request")));
  
  			/* Report status */
  			AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
  #ifdef USE_SYSTEMD
  			sd_notify(0, "STOPPING=1");
  #endif
  
  			if (pmState == PM_STARTUP || pmState == PM_RECOVERY)
  			{
  				/* Just shut down background processes silently */
  				pmState = PM_STOP_BACKENDS;
  			}
  			else if (pmState == PM_RUN ||
  					 pmState == PM_HOT_STANDBY)
  			{
  				/* Report that we're about to zap live client sessions */
  				ereport(LOG,
  						(errmsg("aborting any active transactions")));
  				pmState = PM_STOP_BACKENDS;
  			}
  
  			/*
  			 * PostmasterStateMachine will issue any necessary signals, or
  			 * take the next step if no child processes need to be killed.
  			 */
  			PostmasterStateMachine();
  			break;
  
  		case SIGQUIT:
  
  			/*
  			 * Immediate Shutdown:
  			 *
  			 * abort all children with SIGQUIT, wait for them to exit,
  			 * terminate remaining ones with SIGKILL, then exit without
  			 * attempt to properly shut down the data base system.
  			 */
  			if (Shutdown >= ImmediateShutdown)
  				break;
  			Shutdown = ImmediateShutdown;
  			ereport(LOG,
  					(errmsg("received immediate shutdown request")));
  
  			/* Report status */
  			AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STOPPING);
  #ifdef USE_SYSTEMD
  			sd_notify(0, "STOPPING=1");
  #endif
  
  			/* tell children to shut down ASAP */
  			SetQuitSignalReason(PMQUIT_FOR_STOP);
  			TerminateChildren(SIGQUIT);
  			pmState = PM_WAIT_BACKENDS;
  
  			/* set stopwatch for them to die */
  			AbortStartTime = time(NULL);
  
  			/*
  			 * Now wait for backends to exit.  If there are none,
  			 * PostmasterStateMachine will take the next step.
  			 */
  			PostmasterStateMachine();
  			break;
  	}
  
  #ifdef WIN32
  	PG_SETMASK(&UnBlockSig);
  #endif
  
  	errno = save_errno;
  }
  
  /*
   * Reaper -- signal handler to cleanup after a child process dies.
   */
  static void
  reaper(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  	int			pid;			/* process id of dead child process */
  	int			exitstatus;		/* its exit status */
  
  	/*
  	 * We rely on the signal mechanism to have blocked all signals ... except
  	 * on Windows, which lacks sigaction(), so we have to do it manually.
  	 */
  #ifdef WIN32
  	PG_SETMASK(&BlockSig);
  #endif
  
  	ereport(DEBUG4,
  			(errmsg_internal("reaping dead processes")));
  
  	while ((pid = waitpid(-1, &exitstatus, WNOHANG)) > 0)
  	{
  		/*
  		 * Check if this child was a startup process.
  		 */
  		if (pid == StartupPID)
  		{
  			StartupPID = 0;
  
  			/*
  			 * Startup process exited in response to a shutdown request (or it
  			 * completed normally regardless of the shutdown request).
  			 */
  			if (Shutdown > NoShutdown &&
  				(EXIT_STATUS_0(exitstatus) || EXIT_STATUS_1(exitstatus)))
  			{
  				StartupStatus = STARTUP_NOT_RUNNING;
  				pmState = PM_WAIT_BACKENDS;
  				/* PostmasterStateMachine logic does the rest */
  				continue;
  			}
  
  			if (EXIT_STATUS_3(exitstatus))
  			{
  				ereport(LOG,
  						(errmsg("shutdown at recovery target")));
  				StartupStatus = STARTUP_NOT_RUNNING;
  				Shutdown = Max(Shutdown, SmartShutdown);
  				TerminateChildren(SIGTERM);
  				pmState = PM_WAIT_BACKENDS;
  				/* PostmasterStateMachine logic does the rest */
  				continue;
  			}
  
  			/*
  			 * Unexpected exit of startup process (including FATAL exit)
  			 * during PM_STARTUP is treated as catastrophic. There are no
  			 * other processes running yet, so we can just exit.
  			 */
  			if (pmState == PM_STARTUP &&
  				StartupStatus != STARTUP_SIGNALED &&
  				!EXIT_STATUS_0(exitstatus))
  			{
  				LogChildExit(LOG, _("startup process"),
  							 pid, exitstatus);
  				ereport(LOG,
  						(errmsg("aborting startup due to startup process failure")));
  				ExitPostmaster(1);
  			}
  
  			/*
  			 * After PM_STARTUP, any unexpected exit (including FATAL exit) of
  			 * the startup process is catastrophic, so kill other children,
  			 * and set StartupStatus so we don't try to reinitialize after
  			 * they're gone.  Exception: if StartupStatus is STARTUP_SIGNALED,
  			 * then we previously sent the startup process a SIGQUIT; so
  			 * that's probably the reason it died, and we do want to try to
  			 * restart in that case.
  			 *
  			 * This stanza also handles the case where we sent a SIGQUIT
  			 * during PM_STARTUP due to some dead_end child crashing: in that
  			 * situation, if the startup process dies on the SIGQUIT, we need
  			 * to transition to PM_WAIT_BACKENDS state which will allow
  			 * PostmasterStateMachine to restart the startup process.  (On the
  			 * other hand, the startup process might complete normally, if we
  			 * were too late with the SIGQUIT.  In that case we'll fall
  			 * through and commence normal operations.)
  			 */
  			if (!EXIT_STATUS_0(exitstatus))
  			{
  				if (StartupStatus == STARTUP_SIGNALED)
  				{
  					StartupStatus = STARTUP_NOT_RUNNING;
  					if (pmState == PM_STARTUP)
  						pmState = PM_WAIT_BACKENDS;
  				}
  				else
  					StartupStatus = STARTUP_CRASHED;
  				HandleChildCrash(pid, exitstatus,
  								 _("startup process"));
  				continue;
  			}
  
  			/*
  			 * Startup succeeded, commence normal operations
  			 */
  			StartupStatus = STARTUP_NOT_RUNNING;
  			FatalError = false;
  			AbortStartTime = 0;
  			ReachedNormalRunning = true;
  			pmState = PM_RUN;
  			connsAllowed = true;
  
  			/*
  			 * Crank up the background tasks, if we didn't do that already
  			 * when we entered consistent recovery state.  It doesn't matter
  			 * if this fails, we'll just try again later.
  			 */
  			if (CheckpointerPID == 0)
  				CheckpointerPID = StartCheckpointer();
  			if (BgWriterPID == 0)
  				BgWriterPID = StartBackgroundWriter();
  			if (WalWriterPID == 0)
  				WalWriterPID = StartWalWriter();
  
  			/*
  			 * Likewise, start other special children as needed.  In a restart
  			 * situation, some of them may be alive already.
  			 */
  			if (!IsBinaryUpgrade && AutoVacuumingActive() && AutoVacPID == 0)
  				AutoVacPID = StartAutoVacLauncher();
  			if (PgArchStartupAllowed() && PgArchPID == 0)
  				PgArchPID = StartArchiver();
  
  			/* workers may be scheduled to start now */
  			maybe_start_bgworkers();
  
  			/* at this point we are really open for business */
  			ereport(LOG,
  					(errmsg("database system is ready to accept connections")));
  
  			/* Report status */
  			AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_READY);
  #ifdef USE_SYSTEMD
  			sd_notify(0, "READY=1");
  #endif
  
  			continue;
  		}
  
  		/*
  		 * Was it the bgwriter?  Normal exit can be ignored; we'll start a new
  		 * one at the next iteration of the postmaster's main loop, if
  		 * necessary.  Any other exit condition is treated as a crash.
  		 */
  		if (pid == BgWriterPID)
  		{
  			BgWriterPID = 0;
  			if (!EXIT_STATUS_0(exitstatus))
  				HandleChildCrash(pid, exitstatus,
  								 _("background writer process"));
  			continue;
  		}
  
  		/*
  		 * Was it the checkpointer?
  		 */
  		if (pid == CheckpointerPID)
  		{
  			CheckpointerPID = 0;
  			if (EXIT_STATUS_0(exitstatus) && pmState == PM_SHUTDOWN)
  			{
  				/*
  				 * OK, we saw normal exit of the checkpointer after it's been
  				 * told to shut down.  We expect that it wrote a shutdown
  				 * checkpoint.  (If for some reason it didn't, recovery will
  				 * occur on next postmaster start.)
  				 *
  				 * At this point we should have no normal backend children
  				 * left (else we'd not be in PM_SHUTDOWN state) but we might
  				 * have dead_end children to wait for.
  				 *
  				 * If we have an archiver subprocess, tell it to do a last
  				 * archive cycle and quit. Likewise, if we have walsender
  				 * processes, tell them to send any remaining WAL and quit.
  				 */
  				Assert(Shutdown > NoShutdown);
  
  				/* Waken archiver for the last time */
  				if (PgArchPID != 0)
  					signal_child(PgArchPID, SIGUSR2);
  
  				/*
  				 * Waken walsenders for the last time. No regular backends
  				 * should be around anymore.
  				 */
  				SignalChildren(SIGUSR2);
  
  				pmState = PM_SHUTDOWN_2;
  			}
  			else
  			{
  				/*
  				 * Any unexpected exit of the checkpointer (including FATAL
  				 * exit) is treated as a crash.
  				 */
  				HandleChildCrash(pid, exitstatus,
  								 _("checkpointer process"));
  			}
  
  			continue;
  		}
  
  		/*
  		 * Was it the wal writer?  Normal exit can be ignored; we'll start a
  		 * new one at the next iteration of the postmaster's main loop, if
  		 * necessary.  Any other exit condition is treated as a crash.
  		 */
  		if (pid == WalWriterPID)
  		{
  			WalWriterPID = 0;
  			if (!EXIT_STATUS_0(exitstatus))
  				HandleChildCrash(pid, exitstatus,
  								 _("WAL writer process"));
  			continue;
  		}
  
  		/*
  		 * Was it the wal receiver?  If exit status is zero (normal) or one
  		 * (FATAL exit), we assume everything is all right just like normal
  		 * backends.  (If we need a new wal receiver, we'll start one at the
  		 * next iteration of the postmaster's main loop.)
  		 */
  		if (pid == WalReceiverPID)
  		{
  			WalReceiverPID = 0;
  			if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
  				HandleChildCrash(pid, exitstatus,
  								 _("WAL receiver process"));
  			continue;
  		}
  
  		/*
  		 * Was it the autovacuum launcher?	Normal exit can be ignored; we'll
  		 * start a new one at the next iteration of the postmaster's main
  		 * loop, if necessary.  Any other exit condition is treated as a
  		 * crash.
  		 */
  		if (pid == AutoVacPID)
  		{
  			AutoVacPID = 0;
  			if (!EXIT_STATUS_0(exitstatus))
  				HandleChildCrash(pid, exitstatus,
  								 _("autovacuum launcher process"));
  			continue;
  		}
  
  		/*
  		 * Was it the archiver?  If exit status is zero (normal) or one (FATAL
  		 * exit), we assume everything is all right just like normal backends
  		 * and just try to restart a new one so that we immediately retry
  		 * archiving remaining files. (If fail, we'll try again in future
  		 * cycles of the postmaster's main loop.) Unless we were waiting for
  		 * it to shut down; don't restart it in that case, and
  		 * PostmasterStateMachine() will advance to the next shutdown step.
  		 */
  		if (pid == PgArchPID)
  		{
  			PgArchPID = 0;
  			if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
  				HandleChildCrash(pid, exitstatus,
  								 _("archiver process"));
  			if (PgArchStartupAllowed())
  				PgArchPID = StartArchiver();
  			continue;
  		}
  
  		/* Was it the system logger?  If so, try to start a new one */
  		if (pid == SysLoggerPID)
  		{
  			SysLoggerPID = 0;
  			/* for safety's sake, launch new logger *first* */
  			SysLoggerPID = SysLogger_Start();
  			if (!EXIT_STATUS_0(exitstatus))
  				LogChildExit(LOG, _("system logger process"),
  							 pid, exitstatus);
  			continue;
  		}
  
  		/* Was it one of our background workers? */
  		if (CleanupBackgroundWorker(pid, exitstatus))
  		{
  			/* have it be restarted */
  			HaveCrashedWorker = true;
  			continue;
  		}
  
  		/*
  		 * Else do standard backend child cleanup.
  		 */
  		CleanupBackend(pid, exitstatus);
  	}							/* loop over pending child-death reports */
  
  	/*
  	 * After cleaning out the SIGCHLD queue, see if we have any state changes
  	 * or actions to make.
  	 */
  	PostmasterStateMachine();
  
  	/* Done with signal handler */
  #ifdef WIN32
  	PG_SETMASK(&UnBlockSig);
  #endif
  
  	errno = save_errno;
  }
  
  /*
   * Scan the bgworkers list and see if the given PID (which has just stopped
   * or crashed) is in it.  Handle its shutdown if so, and return true.  If not a
   * bgworker, return false.
   *
   * This is heavily based on CleanupBackend.  One important difference is that
   * we don't know yet that the dying process is a bgworker, so we must be silent
   * until we're sure it is.
   */
  static bool
  CleanupBackgroundWorker(int pid,
  						int exitstatus) /* child's exit status */
  {
  	char		namebuf[MAXPGPATH];
  	slist_mutable_iter iter;
  
  	slist_foreach_modify(iter, &BackgroundWorkerList)
  	{
  		RegisteredBgWorker *rw;
  
  		rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
  
  		if (rw->rw_pid != pid)
  			continue;
  
  #ifdef WIN32
  		/* see CleanupBackend */
  		if (exitstatus == ERROR_WAIT_NO_CHILDREN)
  			exitstatus = 0;
  #endif
  
  		snprintf(namebuf, MAXPGPATH, _("background worker \"%s\""),
  				 rw->rw_worker.bgw_type);
  
  
  		if (!EXIT_STATUS_0(exitstatus))
  		{
  			/* Record timestamp, so we know when to restart the worker. */
  			rw->rw_crashed_at = GetCurrentTimestamp();
  		}
  		else
  		{
  			/* Zero exit status means terminate */
  			rw->rw_crashed_at = 0;
  			rw->rw_terminate = true;
  		}
  
  		/*
  		 * Additionally, just like a backend, any exit status other than 0 or
  		 * 1 is considered a crash and causes a system-wide restart.
  		 */
  		if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
  		{
  			HandleChildCrash(pid, exitstatus, namebuf);
  			return true;
  		}
  
  		/*
  		 * We must release the postmaster child slot. If the worker failed to
  		 * do so, it did not clean up after itself, requiring a crash-restart
  		 * cycle.
  		 */
  		if (!ReleasePostmasterChildSlot(rw->rw_child_slot))
  		{
  			HandleChildCrash(pid, exitstatus, namebuf);
  			return true;
  		}
  
  		/* Get it out of the BackendList and clear out remaining data */
  		dlist_delete(&rw->rw_backend->elem);
  #ifdef EXEC_BACKEND
  		ShmemBackendArrayRemove(rw->rw_backend);
  #endif
  
  		/*
  		 * It's possible that this background worker started some OTHER
  		 * background worker and asked to be notified when that worker started
  		 * or stopped.  If so, cancel any notifications destined for the
  		 * now-dead backend.
  		 */
  		if (rw->rw_backend->bgworker_notify)
  			BackgroundWorkerStopNotifications(rw->rw_pid);
  		free(rw->rw_backend);
  		rw->rw_backend = NULL;
  		rw->rw_pid = 0;
  		rw->rw_child_slot = 0;
  		ReportBackgroundWorkerExit(&iter);	/* report child death */
  
  		LogChildExit(EXIT_STATUS_0(exitstatus) ? DEBUG1 : LOG,
  					 namebuf, pid, exitstatus);
  
  		return true;
  	}
  
  	return false;
  }
  
  /*
   * CleanupBackend -- cleanup after terminated backend.
   *
   * Remove all local state associated with backend.
   *
   * If you change this, see also CleanupBackgroundWorker.
   */
  static void
  CleanupBackend(int pid,
  			   int exitstatus)	/* child's exit status. */
  {
  	dlist_mutable_iter iter;
  
  	LogChildExit(DEBUG2, _("server process"), pid, exitstatus);
  
  	/*
  	 * If a backend dies in an ugly way then we must signal all other backends
  	 * to quickdie.  If exit status is zero (normal) or one (FATAL exit), we
  	 * assume everything is all right and proceed to remove the backend from
  	 * the active backend list.
  	 */
  
  #ifdef WIN32
  
  	/*
  	 * On win32, also treat ERROR_WAIT_NO_CHILDREN (128) as nonfatal case,
  	 * since that sometimes happens under load when the process fails to start
  	 * properly (long before it starts using shared memory). Microsoft reports
  	 * it is related to mutex failure:
  	 * http://archives.postgresql.org/pgsql-hackers/2010-09/msg00790.php
  	 */
  	if (exitstatus == ERROR_WAIT_NO_CHILDREN)
  	{
  		LogChildExit(LOG, _("server process"), pid, exitstatus);
  		exitstatus = 0;
  	}
  #endif
  
  	if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
  	{
  		HandleChildCrash(pid, exitstatus, _("server process"));
  		return;
  	}
  
  	dlist_foreach_modify(iter, &BackendList)
  	{
  		Backend    *bp = dlist_container(Backend, elem, iter.cur);
  
  		if (bp->pid == pid)
  		{
  			if (!bp->dead_end)
  			{
  				if (!ReleasePostmasterChildSlot(bp->child_slot))
  				{
  					/*
  					 * Uh-oh, the child failed to clean itself up.  Treat as a
  					 * crash after all.
  					 */
  					HandleChildCrash(pid, exitstatus, _("server process"));
  					return;
  				}
  #ifdef EXEC_BACKEND
  				ShmemBackendArrayRemove(bp);
  #endif
  			}
  			if (bp->bgworker_notify)
  			{
  				/*
  				 * This backend may have been slated to receive SIGUSR1 when
  				 * some background worker started or stopped.  Cancel those
  				 * notifications, as we don't want to signal PIDs that are not
  				 * PostgreSQL backends.  This gets skipped in the (probably
  				 * very common) case where the backend has never requested any
  				 * such notifications.
  				 */
  				BackgroundWorkerStopNotifications(bp->pid);
  			}
  			dlist_delete(iter.cur);
  			free(bp);
  			break;
  		}
  	}
  }
  
  /*
   * HandleChildCrash -- cleanup after failed backend, bgwriter, checkpointer,
   * walwriter, autovacuum, archiver or background worker.
   *
   * The objectives here are to clean up our local state about the child
   * process, and to signal all other remaining children to quickdie.
   */
  static void
  HandleChildCrash(int pid, int exitstatus, const char *procname)
  {
  	dlist_mutable_iter iter;
  	slist_iter	siter;
  	Backend    *bp;
  	bool		take_action;
  
  	/*
  	 * We only log messages and send signals if this is the first process
  	 * crash and we're not doing an immediate shutdown; otherwise, we're only
  	 * here to update postmaster's idea of live processes.  If we have already
  	 * signaled children, nonzero exit status is to be expected, so don't
  	 * clutter log.
  	 */
  	take_action = !FatalError && Shutdown != ImmediateShutdown;
  
  	if (take_action)
  	{
  		LogChildExit(LOG, procname, pid, exitstatus);
  		ereport(LOG,
  				(errmsg("terminating any other active server processes")));
  		SetQuitSignalReason(PMQUIT_FOR_CRASH);
  	}
  
  	/* Process background workers. */
  	slist_foreach(siter, &BackgroundWorkerList)
  	{
  		RegisteredBgWorker *rw;
  
  		rw = slist_container(RegisteredBgWorker, rw_lnode, siter.cur);
  		if (rw->rw_pid == 0)
  			continue;			/* not running */
  		if (rw->rw_pid == pid)
  		{
  			/*
  			 * Found entry for freshly-dead worker, so remove it.
  			 */
  			(void) ReleasePostmasterChildSlot(rw->rw_child_slot);
  			dlist_delete(&rw->rw_backend->elem);
  #ifdef EXEC_BACKEND
  			ShmemBackendArrayRemove(rw->rw_backend);
  #endif
  			free(rw->rw_backend);
  			rw->rw_backend = NULL;
  			rw->rw_pid = 0;
  			rw->rw_child_slot = 0;
  			/* don't reset crashed_at */
  			/* don't report child stop, either */
  			/* Keep looping so we can signal remaining workers */
  		}
  		else
  		{
  			/*
  			 * This worker is still alive.  Unless we did so already, tell it
  			 * to commit hara-kiri.
  			 *
  			 * SIGQUIT is the special signal that says exit without proc_exit
  			 * and let the user know what's going on. But if SendStop is set
  			 * (-T on command line), then we send SIGSTOP instead, so that we
  			 * can get core dumps from all backends by hand.
  			 */
  			if (take_action)
  			{
  				ereport(DEBUG2,
  						(errmsg_internal("sending %s to process %d",
  										 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  										 (int) rw->rw_pid)));
  				signal_child(rw->rw_pid, (SendStop ? SIGSTOP : SIGQUIT));
  			}
  		}
  	}
  
  	/* Process regular backends */
  	dlist_foreach_modify(iter, &BackendList)
  	{
  		bp = dlist_container(Backend, elem, iter.cur);
  
  		if (bp->pid == pid)
  		{
  			/*
  			 * Found entry for freshly-dead backend, so remove it.
  			 */
  			if (!bp->dead_end)
  			{
  				(void) ReleasePostmasterChildSlot(bp->child_slot);
  #ifdef EXEC_BACKEND
  				ShmemBackendArrayRemove(bp);
  #endif
  			}
  			dlist_delete(iter.cur);
  			free(bp);
  			/* Keep looping so we can signal remaining backends */
  		}
  		else
  		{
  			/*
  			 * This backend is still alive.  Unless we did so already, tell it
  			 * to commit hara-kiri.
  			 *
  			 * SIGQUIT is the special signal that says exit without proc_exit
  			 * and let the user know what's going on. But if SendStop is set
  			 * (-T on command line), then we send SIGSTOP instead, so that we
  			 * can get core dumps from all backends by hand.
  			 *
  			 * We could exclude dead_end children here, but at least in the
  			 * SIGSTOP case it seems better to include them.
  			 *
  			 * Background workers were already processed above; ignore them
  			 * here.
  			 */
  			if (bp->bkend_type == BACKEND_TYPE_BGWORKER)
  				continue;
  
  			if (take_action)
  			{
  				ereport(DEBUG2,
  						(errmsg_internal("sending %s to process %d",
  										 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  										 (int) bp->pid)));
  				signal_child(bp->pid, (SendStop ? SIGSTOP : SIGQUIT));
  			}
  		}
  	}
  
  	/* Take care of the startup process too */
  	if (pid == StartupPID)
  	{
  		StartupPID = 0;
  		/* Caller adjusts StartupStatus, so don't touch it here */
  	}
  	else if (StartupPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) StartupPID)));
  		signal_child(StartupPID, (SendStop ? SIGSTOP : SIGQUIT));
  		StartupStatus = STARTUP_SIGNALED;
  	}
  
  	/* Take care of the bgwriter too */
  	if (pid == BgWriterPID)
  		BgWriterPID = 0;
  	else if (BgWriterPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) BgWriterPID)));
  		signal_child(BgWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
  	/* Take care of the checkpointer too */
  	if (pid == CheckpointerPID)
  		CheckpointerPID = 0;
  	else if (CheckpointerPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) CheckpointerPID)));
  		signal_child(CheckpointerPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
  	/* Take care of the walwriter too */
  	if (pid == WalWriterPID)
  		WalWriterPID = 0;
  	else if (WalWriterPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) WalWriterPID)));
  		signal_child(WalWriterPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
  	/* Take care of the walreceiver too */
  	if (pid == WalReceiverPID)
  		WalReceiverPID = 0;
  	else if (WalReceiverPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) WalReceiverPID)));
  		signal_child(WalReceiverPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
  	/* Take care of the autovacuum launcher too */
  	if (pid == AutoVacPID)
  		AutoVacPID = 0;
  	else if (AutoVacPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) AutoVacPID)));
  		signal_child(AutoVacPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
  	/* Take care of the archiver too */
  	if (pid == PgArchPID)
  		PgArchPID = 0;
  	else if (PgArchPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 (SendStop ? "SIGSTOP" : "SIGQUIT"),
  								 (int) PgArchPID)));
  		signal_child(PgArchPID, (SendStop ? SIGSTOP : SIGQUIT));
  	}
  
  	/* We do NOT restart the syslogger */
  
  	if (Shutdown != ImmediateShutdown)
  		FatalError = true;
  
  	/* We now transit into a state of waiting for children to die */
  	if (pmState == PM_RECOVERY ||
  		pmState == PM_HOT_STANDBY ||
  		pmState == PM_RUN ||
  		pmState == PM_STOP_BACKENDS ||
  		pmState == PM_SHUTDOWN)
  		pmState = PM_WAIT_BACKENDS;
  
  	/*
  	 * .. and if this doesn't happen quickly enough, now the clock is ticking
  	 * for us to kill them without mercy.
  	 */
  	if (AbortStartTime == 0)
  		AbortStartTime = time(NULL);
  }
  
  /*
   * Log the death of a child process.
   */
  static void
  LogChildExit(int lev, const char *procname, int pid, int exitstatus)
  {
  	/*
  	 * size of activity_buffer is arbitrary, but set equal to default
  	 * track_activity_query_size
  	 */
  	char		activity_buffer[1024];
  	const char *activity = NULL;
  
  	if (!EXIT_STATUS_0(exitstatus))
  		activity = pgstat_get_crashed_backend_activity(pid,
  													   activity_buffer,
  													   sizeof(activity_buffer));
  
  	if (WIFEXITED(exitstatus))
  		ereport(lev,
  
  		/*------
  		  translator: %s is a noun phrase describing a child process, such as
  		  "server process" */
  				(errmsg("%s (PID %d) exited with exit code %d",
  						procname, pid, WEXITSTATUS(exitstatus)),
  				 activity ? errdetail("Failed process was running: %s", activity) : 0));
  	else if (WIFSIGNALED(exitstatus))
  	{
  #if defined(WIN32)
  		ereport(lev,
  
  		/*------
  		  translator: %s is a noun phrase describing a child process, such as
  		  "server process" */
  				(errmsg("%s (PID %d) was terminated by exception 0x%X",
  						procname, pid, WTERMSIG(exitstatus)),
  				 errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value."),
  				 activity ? errdetail("Failed process was running: %s", activity) : 0));
  #else
  		ereport(lev,
  
  		/*------
  		  translator: %s is a noun phrase describing a child process, such as
  		  "server process" */
  				(errmsg("%s (PID %d) was terminated by signal %d: %s",
  						procname, pid, WTERMSIG(exitstatus),
  						pg_strsignal(WTERMSIG(exitstatus))),
  				 activity ? errdetail("Failed process was running: %s", activity) : 0));
  #endif
  	}
  	else
  		ereport(lev,
  
  		/*------
  		  translator: %s is a noun phrase describing a child process, such as
  		  "server process" */
  				(errmsg("%s (PID %d) exited with unrecognized status %d",
  						procname, pid, exitstatus),
  				 activity ? errdetail("Failed process was running: %s", activity) : 0));
  }
  
  /*
   * Advance the postmaster's state machine and take actions as appropriate
   *
   * This is common code for pmdie(), reaper() and sigusr1_handler(), which
   * receive the signals that might mean we need to change state.
   */
  static void
  PostmasterStateMachine(void)
  {
  	/* If we're doing a smart shutdown, try to advance that state. */
  	if (pmState == PM_RUN || pmState == PM_HOT_STANDBY)
  	{
  		if (!connsAllowed)
  		{
  			/*
  			 * This state ends when we have no normal client backends running.
  			 * Then we're ready to stop other children.
  			 */
  			if (CountChildren(BACKEND_TYPE_NORMAL) == 0)
  				pmState = PM_STOP_BACKENDS;
  		}
  	}
  
  	/*
  	 * If we're ready to do so, signal child processes to shut down.  (This
  	 * isn't a persistent state, but treating it as a distinct pmState allows
  	 * us to share this code across multiple shutdown code paths.)
  	 */
  	if (pmState == PM_STOP_BACKENDS)
  	{
  		/*
  		 * Forget any pending requests for background workers, since we're no
  		 * longer willing to launch any new workers.  (If additional requests
  		 * arrive, BackgroundWorkerStateChange will reject them.)
  		 */
  		ForgetUnstartedBackgroundWorkers();
  
  		/* Signal all backend children except walsenders */
  		SignalSomeChildren(SIGTERM,
  						   BACKEND_TYPE_ALL - BACKEND_TYPE_WALSND);
  		/* and the autovac launcher too */
  		if (AutoVacPID != 0)
  			signal_child(AutoVacPID, SIGTERM);
  		/* and the bgwriter too */
  		if (BgWriterPID != 0)
  			signal_child(BgWriterPID, SIGTERM);
  		/* and the walwriter too */
  		if (WalWriterPID != 0)
  			signal_child(WalWriterPID, SIGTERM);
  		/* If we're in recovery, also stop startup and walreceiver procs */
  		if (StartupPID != 0)
  			signal_child(StartupPID, SIGTERM);
  		if (WalReceiverPID != 0)
  			signal_child(WalReceiverPID, SIGTERM);
  		/* checkpointer, archiver, stats, and syslogger may continue for now */
  
  		/* Now transition to PM_WAIT_BACKENDS state to wait for them to die */
  		pmState = PM_WAIT_BACKENDS;
  	}
  
  	/*
  	 * If we are in a state-machine state that implies waiting for backends to
  	 * exit, see if they're all gone, and change state if so.
  	 */
  	if (pmState == PM_WAIT_BACKENDS)
  	{
  		/*
  		 * PM_WAIT_BACKENDS state ends when we have no regular backends
  		 * (including autovac workers), no bgworkers (including unconnected
  		 * ones), and no walwriter, autovac launcher or bgwriter.  If we are
  		 * doing crash recovery or an immediate shutdown then we expect the
  		 * checkpointer to exit as well, otherwise not. The stats and
  		 * syslogger processes are disregarded since they are not connected to
  		 * shared memory; we also disregard dead_end children here. Walsenders
  		 * and archiver are also disregarded, they will be terminated later
  		 * after writing the checkpoint record.
  		 */
  		if (CountChildren(BACKEND_TYPE_ALL - BACKEND_TYPE_WALSND) == 0 &&
  			StartupPID == 0 &&
  			WalReceiverPID == 0 &&
  			BgWriterPID == 0 &&
  			(CheckpointerPID == 0 ||
  			 (!FatalError && Shutdown < ImmediateShutdown)) &&
  			WalWriterPID == 0 &&
  			AutoVacPID == 0)
  		{
  			if (Shutdown >= ImmediateShutdown || FatalError)
  			{
  				/*
  				 * Start waiting for dead_end children to die.  This state
  				 * change causes ServerLoop to stop creating new ones.
  				 */
  				pmState = PM_WAIT_DEAD_END;
  
  				/*
  				 * We already SIGQUIT'd the archiver and stats processes, if
  				 * any, when we started immediate shutdown or entered
  				 * FatalError state.
  				 */
  			}
  			else
  			{
  				/*
  				 * If we get here, we are proceeding with normal shutdown. All
  				 * the regular children are gone, and it's time to tell the
  				 * checkpointer to do a shutdown checkpoint.
  				 */
  				Assert(Shutdown > NoShutdown);
  				/* Start the checkpointer if not running */
  				if (CheckpointerPID == 0)
  					CheckpointerPID = StartCheckpointer();
  				/* And tell it to shut down */
  				if (CheckpointerPID != 0)
  				{
  					signal_child(CheckpointerPID, SIGUSR2);
  					pmState = PM_SHUTDOWN;
  				}
  				else
  				{
  					/*
  					 * If we failed to fork a checkpointer, just shut down.
  					 * Any required cleanup will happen at next restart. We
  					 * set FatalError so that an "abnormal shutdown" message
  					 * gets logged when we exit.
  					 */
  					FatalError = true;
  					pmState = PM_WAIT_DEAD_END;
  
  					/* Kill the walsenders and archiver too */
  					SignalChildren(SIGQUIT);
  					if (PgArchPID != 0)
  						signal_child(PgArchPID, SIGQUIT);
  				}
  			}
  		}
  	}
  
  	if (pmState == PM_SHUTDOWN_2)
  	{
  		/*
  		 * PM_SHUTDOWN_2 state ends when there's no other children than
  		 * dead_end children left. There shouldn't be any regular backends
  		 * left by now anyway; what we're really waiting for is walsenders and
  		 * archiver.
  		 */
  		if (PgArchPID == 0 && CountChildren(BACKEND_TYPE_ALL) == 0)
  		{
  			pmState = PM_WAIT_DEAD_END;
  		}
  	}
  
  	if (pmState == PM_WAIT_DEAD_END)
  	{
  		/*
  		 * PM_WAIT_DEAD_END state ends when the BackendList is entirely empty
  		 * (ie, no dead_end children remain), and the archiver is gone too.
  		 *
  		 * The reason we wait for those two is to protect them against a new
  		 * postmaster starting conflicting subprocesses; this isn't an
  		 * ironclad protection, but it at least helps in the
  		 * shutdown-and-immediately-restart scenario.  Note that they have
  		 * already been sent appropriate shutdown signals, either during a
  		 * normal state transition leading up to PM_WAIT_DEAD_END, or during
  		 * FatalError processing.
  		 */
  		if (dlist_is_empty(&BackendList) && PgArchPID == 0)
  		{
  			/* These other guys should be dead already */
  			Assert(StartupPID == 0);
  			Assert(WalReceiverPID == 0);
  			Assert(BgWriterPID == 0);
  			Assert(CheckpointerPID == 0);
  			Assert(WalWriterPID == 0);
  			Assert(AutoVacPID == 0);
  			/* syslogger is not considered here */
  			pmState = PM_NO_CHILDREN;
  		}
  	}
  
  	/*
  	 * If we've been told to shut down, we exit as soon as there are no
  	 * remaining children.  If there was a crash, cleanup will occur at the
  	 * next startup.  (Before PostgreSQL 8.3, we tried to recover from the
  	 * crash before exiting, but that seems unwise if we are quitting because
  	 * we got SIGTERM from init --- there may well not be time for recovery
  	 * before init decides to SIGKILL us.)
  	 *
  	 * Note that the syslogger continues to run.  It will exit when it sees
  	 * EOF on its input pipe, which happens when there are no more upstream
  	 * processes.
  	 */
  	if (Shutdown > NoShutdown && pmState == PM_NO_CHILDREN)
  	{
  		if (FatalError)
  		{
  			ereport(LOG, (errmsg("abnormal database system shutdown")));
  			ExitPostmaster(1);
  		}
  		else
  		{
  			/*
  			 * Normal exit from the postmaster is here.  We don't need to log
  			 * anything here, since the UnlinkLockFiles proc_exit callback
  			 * will do so, and that should be the last user-visible action.
  			 */
  			ExitPostmaster(0);
  		}
  	}
  
  	/*
  	 * If the startup process failed, or the user does not want an automatic
  	 * restart after backend crashes, wait for all non-syslogger children to
  	 * exit, and then exit postmaster.  We don't try to reinitialize when the
  	 * startup process fails, because more than likely it will just fail again
  	 * and we will keep trying forever.
  	 */
  	if (pmState == PM_NO_CHILDREN)
  	{
  		if (StartupStatus == STARTUP_CRASHED)
  		{
  			ereport(LOG,
  					(errmsg("shutting down due to startup process failure")));
  			ExitPostmaster(1);
  		}
  		if (!restart_after_crash)
  		{
  			ereport(LOG,
  					(errmsg("shutting down because restart_after_crash is off")));
  			ExitPostmaster(1);
  		}
  	}
  
  	/*
  	 * If we need to recover from a crash, wait for all non-syslogger children
  	 * to exit, then reset shmem and StartupDataBase.
  	 */
  	if (FatalError && pmState == PM_NO_CHILDREN)
  	{
  		ereport(LOG,
  				(errmsg("all server processes terminated; reinitializing")));
  
  		/* remove leftover temporary files after a crash */
  		if (remove_temp_files_after_crash)
  			RemovePgTempFiles();
  
  		/* allow background workers to immediately restart */
  		ResetBackgroundWorkerCrashTimes();
  
  		shmem_exit(1);
  
  		/* re-read control file into local memory */
  		LocalProcessControlFile(true);
  
  		reset_shared();
  
  		StartupPID = StartupDataBase();
  		Assert(StartupPID != 0);
  		StartupStatus = STARTUP_RUNNING;
  		pmState = PM_STARTUP;
  		/* crash recovery started, reset SIGKILL flag */
  		AbortStartTime = 0;
  	}
  }
  
  
  /*
   * Send a signal to a postmaster child process
   *
   * On systems that have setsid(), each child process sets itself up as a
   * process group leader.  For signals that are generally interpreted in the
   * appropriate fashion, we signal the entire process group not just the
   * direct child process.  This allows us to, for example, SIGQUIT a blocked
   * archive_recovery script, or SIGINT a script being run by a backend via
   * system().
   *
   * There is a race condition for recently-forked children: they might not
   * have executed setsid() yet.  So we signal the child directly as well as
   * the group.  We assume such a child will handle the signal before trying
   * to spawn any grandchild processes.  We also assume that signaling the
   * child twice will not cause any problems.
   */
  static void
  signal_child(pid_t pid, int signal)
  {
  	if (kill(pid, signal) < 0)
  		elog(DEBUG3, "kill(%ld,%d) failed: %m", (long) pid, signal);
  #ifdef HAVE_SETSID
  	switch (signal)
  	{
  		case SIGINT:
  		case SIGTERM:
  		case SIGQUIT:
  		case SIGSTOP:
  		case SIGKILL:
  			if (kill(-pid, signal) < 0)
  				elog(DEBUG3, "kill(%ld,%d) failed: %m", (long) (-pid), signal);
  			break;
  		default:
  			break;
  	}
  #endif
  }
  
  /*
   * Send a signal to the targeted children (but NOT special children;
   * dead_end children are never signaled, either).
   */
  static bool
  SignalSomeChildren(int signal, int target)
  {
  	dlist_iter	iter;
  	bool		signaled = false;
  
  	dlist_foreach(iter, &BackendList)
  	{
  		Backend    *bp = dlist_container(Backend, elem, iter.cur);
  
  		if (bp->dead_end)
  			continue;
  
  		/*
  		 * Since target == BACKEND_TYPE_ALL is the most common case, we test
  		 * it first and avoid touching shared memory for every child.
  		 */
  		if (target != BACKEND_TYPE_ALL)
  		{
  			/*
  			 * Assign bkend_type for any recently announced WAL Sender
  			 * processes.
  			 */
  			if (bp->bkend_type == BACKEND_TYPE_NORMAL &&
  				IsPostmasterChildWalSender(bp->child_slot))
  				bp->bkend_type = BACKEND_TYPE_WALSND;
  
  			if (!(target & bp->bkend_type))
  				continue;
  		}
  
  		ereport(DEBUG4,
  				(errmsg_internal("sending signal %d to process %d",
  								 signal, (int) bp->pid)));
  		signal_child(bp->pid, signal);
  		signaled = true;
  	}
  	return signaled;
  }
  
  /*
   * Send a termination signal to children.  This considers all of our children
   * processes, except syslogger and dead_end backends.
   */
  static void
  TerminateChildren(int signal)
  {
  	SignalChildren(signal);
  	if (StartupPID != 0)
  	{
  		signal_child(StartupPID, signal);
  		if (signal == SIGQUIT || signal == SIGKILL)
  			StartupStatus = STARTUP_SIGNALED;
  	}
  	if (BgWriterPID != 0)
  		signal_child(BgWriterPID, signal);
  	if (CheckpointerPID != 0)
  		signal_child(CheckpointerPID, signal);
  	if (WalWriterPID != 0)
  		signal_child(WalWriterPID, signal);
  	if (WalReceiverPID != 0)
  		signal_child(WalReceiverPID, signal);
  	if (AutoVacPID != 0)
  		signal_child(AutoVacPID, signal);
  	if (PgArchPID != 0)
  		signal_child(PgArchPID, signal);
  }
  
  /*
   * BackendStartup -- start backend process
   *
   * returns: STATUS_ERROR if the fork failed, STATUS_OK otherwise.
   *
   * Note: if you change this code, also consider StartAutovacuumWorker.
   */
  static int
  BackendStartup(Port *port)
  {
  	Backend    *bn;				/* for backend cleanup */
  	pid_t		pid;
  
  	/*
  	 * Create backend data structure.  Better before the fork() so we can
  	 * handle failure cleanly.
  	 */
  	bn = (Backend *) malloc(sizeof(Backend));
  	if (!bn)
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  		return STATUS_ERROR;
  	}
  
  	/*
  	 * Compute the cancel key that will be assigned to this backend. The
  	 * backend will have its own copy in the forked-off process' value of
  	 * MyCancelKey, so that it can transmit the key to the frontend.
  	 */
  	if (!RandomCancelKey(&MyCancelKey))
  	{
  		free(bn);
  		ereport(LOG,
  				(errcode(ERRCODE_INTERNAL_ERROR),
  				 errmsg("could not generate random cancel key")));
  		return STATUS_ERROR;
  	}
  
  	bn->cancel_key = MyCancelKey;
  
  	/* Pass down canAcceptConnections state */
  	port->canAcceptConnections = canAcceptConnections(BACKEND_TYPE_NORMAL);
  	bn->dead_end = (port->canAcceptConnections != CAC_OK);
  
  	/*
  	 * Unless it's a dead_end child, assign it a child slot number
  	 */
  	if (!bn->dead_end)
  		bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
  	else
  		bn->child_slot = 0;
  
  	/* Hasn't asked to be notified about any bgworkers yet */
  	bn->bgworker_notify = false;
  
  #ifdef EXEC_BACKEND
  	pid = backend_forkexec(port);
  #else							/* !EXEC_BACKEND */
  	pid = fork_process();
  	if (pid == 0)				/* child */
  	{
  		free(bn);
  
  		/* Detangle from postmaster */
  		InitPostmasterChild();
  
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Perform additional initialization and collect startup packet */
  		BackendInitialize(port);
  
  		/*
  		 * Create a per-backend PGPROC struct in shared memory. We must do
  		 * this before we can use LWLocks. In the !EXEC_BACKEND case (here)
  		 * this could be delayed a bit further, but EXEC_BACKEND needs to do
  		 * stuff with LWLocks before PostgresMain(), so we do it here as well
  		 * for symmetry.
  		 */
  		InitProcess();
  
  		/* And run the backend */
  		BackendRun(port);
  	}
  #endif							/* EXEC_BACKEND */
  
  	if (pid < 0)
  	{
  		/* in parent, fork failed */
  		int			save_errno = errno;
  
  		if (!bn->dead_end)
  			(void) ReleasePostmasterChildSlot(bn->child_slot);
  		free(bn);
  		errno = save_errno;
  		ereport(LOG,
  				(errmsg("could not fork new process for connection: %m")));
  		report_fork_failure_to_client(port, save_errno);
  		return STATUS_ERROR;
  	}
  
  	/* in parent, successful fork */
  	ereport(DEBUG2,
  			(errmsg_internal("forked new backend, pid=%d socket=%d",
  							 (int) pid, (int) port->sock)));
  
  	/*
  	 * Everything's been successful, it's safe to add this backend to our list
  	 * of backends.
  	 */
  	bn->pid = pid;
  	bn->bkend_type = BACKEND_TYPE_NORMAL;	/* Can change later to WALSND */
  	dlist_push_head(&BackendList, &bn->elem);
  
  #ifdef EXEC_BACKEND
  	if (!bn->dead_end)
  		ShmemBackendArrayAdd(bn);
  #endif
  
  	return STATUS_OK;
  }
  
  /*
   * Try to report backend fork() failure to client before we close the
   * connection.  Since we do not care to risk blocking the postmaster on
   * this connection, we set the connection to non-blocking and try only once.
   *
   * This is grungy special-purpose code; we cannot use backend libpq since
   * it's not up and running.
   */
  static void
  report_fork_failure_to_client(Port *port, int errnum)
  {
  	char		buffer[1000];
  	int			rc;
  
  	/* Format the error message packet (always V2 protocol) */
  	snprintf(buffer, sizeof(buffer), "E%s%s\n",
  			 _("could not fork new process for connection: "),
  			 strerror(errnum));
  
  	/* Set port to non-blocking.  Don't do send() if this fails */
  	if (!pg_set_noblock(port->sock))
  		return;
  
  	/* We'll retry after EINTR, but ignore all other failures */
  	do
  	{
  		rc = send(port->sock, buffer, strlen(buffer) + 1, 0);
  	} while (rc < 0 && errno == EINTR);
  }
  
  
  /*
   * BackendInitialize -- initialize an interactive (postmaster-child)
   *				backend process, and collect the client's startup packet.
   *
   * returns: nothing.  Will not return at all if there's any failure.
   *
   * Note: this code does not depend on having any access to shared memory.
   * Indeed, our approach to SIGTERM/timeout handling *requires* that
   * shared memory not have been touched yet; see comments within.
   * In the EXEC_BACKEND case, we are physically attached to shared memory
   * but have not yet set up most of our local pointers to shmem structures.
   */
  static void
  BackendInitialize(Port *port)
  {
  	int			status;
  	int			ret;
  	char		remote_host[NI_MAXHOST];
  	char		remote_port[NI_MAXSERV];
  	StringInfoData ps_data;
  
  	/* Save port etc. for ps status */
  	MyProcPort = port;
  
  	/* Tell fd.c about the long-lived FD associated with the port */
  	ReserveExternalFD();
  
  	/*
  	 * PreAuthDelay is a debugging aid for investigating problems in the
  	 * authentication cycle: it can be set in postgresql.conf to allow time to
  	 * attach to the newly-forked backend with a debugger.  (See also
  	 * PostAuthDelay, which we allow clients to pass through PGOPTIONS, but it
  	 * is not honored until after authentication.)
  	 */
  	if (PreAuthDelay > 0)
  		pg_usleep(PreAuthDelay * 1000000L);
  
  	/* This flag will remain set until InitPostgres finishes authentication */
  	ClientAuthInProgress = true;	/* limit visibility of log messages */
  
  	/* set these to empty in case they are needed before we set them up */
  	port->remote_host = "";
  	port->remote_port = "";
  
  	/*
  	 * Initialize libpq and enable reporting of ereport errors to the client.
  	 * Must do this now because authentication uses libpq to send messages.
  	 */
  	pq_init();					/* initialize libpq to talk to client */
  	whereToSendOutput = DestRemote; /* now safe to ereport to client */
  
  	/*
  	 * We arrange to do _exit(1) if we receive SIGTERM or timeout while trying
  	 * to collect the startup packet; while SIGQUIT results in _exit(2).
  	 * Otherwise the postmaster cannot shutdown the database FAST or IMMED
  	 * cleanly if a buggy client fails to send the packet promptly.
  	 *
  	 * Exiting with _exit(1) is only possible because we have not yet touched
  	 * shared memory; therefore no outside-the-process state needs to get
  	 * cleaned up.
  	 */
  	pqsignal(SIGTERM, process_startup_packet_die);
  	/* SIGQUIT handler was already set up by InitPostmasterChild */
  	InitializeTimeouts();		/* establishes SIGALRM handler */
  	PG_SETMASK(&StartupBlockSig);
  
  	/*
  	 * Get the remote host name and port for logging and status display.
  	 */
  	remote_host[0] = '\0';
  	remote_port[0] = '\0';
  	if ((ret = pg_getnameinfo_all(&port->raddr.addr, port->raddr.salen,
  								  remote_host, sizeof(remote_host),
  								  remote_port, sizeof(remote_port),
  								  (log_hostname ? 0 : NI_NUMERICHOST) | NI_NUMERICSERV)) != 0)
  		ereport(WARNING,
  				(errmsg_internal("pg_getnameinfo_all() failed: %s",
  								 gai_strerror(ret))));
  
  	/*
  	 * Save remote_host and remote_port in port structure (after this, they
  	 * will appear in log_line_prefix data for log messages).
  	 */
  	port->remote_host = strdup(remote_host);
  	port->remote_port = strdup(remote_port);
  
  	/* And now we can issue the Log_connections message, if wanted */
  	if (Log_connections)
  	{
  		if (remote_port[0])
  			ereport(LOG,
  					(errmsg("connection received: host=%s port=%s",
  							remote_host,
  							remote_port)));
  		else
  			ereport(LOG,
  					(errmsg("connection received: host=%s",
  							remote_host)));
  	}
  
  	/*
  	 * If we did a reverse lookup to name, we might as well save the results
  	 * rather than possibly repeating the lookup during authentication.
  	 *
  	 * Note that we don't want to specify NI_NAMEREQD above, because then we'd
  	 * get nothing useful for a client without an rDNS entry.  Therefore, we
  	 * must check whether we got a numeric IPv4 or IPv6 address, and not save
  	 * it into remote_hostname if so.  (This test is conservative and might
  	 * sometimes classify a hostname as numeric, but an error in that
  	 * direction is safe; it only results in a possible extra lookup.)
  	 */
  	if (log_hostname &&
  		ret == 0 &&
  		strspn(remote_host, "0123456789.") < strlen(remote_host) &&
  		strspn(remote_host, "0123456789ABCDEFabcdef:") < strlen(remote_host))
  		port->remote_hostname = strdup(remote_host);
  
  	/*
  	 * Ready to begin client interaction.  We will give up and _exit(1) after
  	 * a time delay, so that a broken client can't hog a connection
  	 * indefinitely.  PreAuthDelay and any DNS interactions above don't count
  	 * against the time limit.
  	 *
  	 * Note: AuthenticationTimeout is applied here while waiting for the
  	 * startup packet, and then again in InitPostgres for the duration of any
  	 * authentication operations.  So a hostile client could tie up the
  	 * process for nearly twice AuthenticationTimeout before we kick him off.
  	 *
  	 * Note: because PostgresMain will call InitializeTimeouts again, the
  	 * registration of STARTUP_PACKET_TIMEOUT will be lost.  This is okay
  	 * since we never use it again after this function.
  	 */
  	RegisterTimeout(STARTUP_PACKET_TIMEOUT, StartupPacketTimeoutHandler);
  	enable_timeout_after(STARTUP_PACKET_TIMEOUT, AuthenticationTimeout * 1000);
  
  	/*
  	 * Receive the startup packet (which might turn out to be a cancel request
  	 * packet).
  	 */
  	status = ProcessStartupPacket(port, false, false);
  
  	/*
  	 * Disable the timeout, and prevent SIGTERM again.
  	 */
  	disable_timeout(STARTUP_PACKET_TIMEOUT, false);
  	PG_SETMASK(&BlockSig);
  
  	/*
  	 * As a safety check that nothing in startup has yet performed
  	 * shared-memory modifications that would need to be undone if we had
  	 * exited through SIGTERM or timeout above, check that no on_shmem_exit
  	 * handlers have been registered yet.  (This isn't terribly bulletproof,
  	 * since someone might misuse an on_proc_exit handler for shmem cleanup,
  	 * but it's a cheap and helpful check.  We cannot disallow on_proc_exit
  	 * handlers unfortunately, since pq_init() already registered one.)
  	 */
  	check_on_shmem_exit_lists_are_empty();
  
  	/*
  	 * Stop here if it was bad or a cancel packet.  ProcessStartupPacket
  	 * already did any appropriate error reporting.
  	 */
  	if (status != STATUS_OK)
  		proc_exit(0);
  
  	/*
  	 * Now that we have the user and database name, we can set the process
  	 * title for ps.  It's good to do this as early as possible in startup.
  	 */
  	initStringInfo(&ps_data);
  	if (am_walsender)
  		appendStringInfo(&ps_data, "%s ", GetBackendTypeDesc(B_WAL_SENDER));
  	appendStringInfo(&ps_data, "%s ", port->user_name);
  	if (!am_walsender)
  		appendStringInfo(&ps_data, "%s ", port->database_name);
  	appendStringInfo(&ps_data, "%s", port->remote_host);
  	if (port->remote_port[0] != '\0')
  		appendStringInfo(&ps_data, "(%s)", port->remote_port);
  
  	init_ps_display(ps_data.data);
  	pfree(ps_data.data);
  
  	set_ps_display("initializing");
  }
  
  
  /*
   * BackendRun -- set up the backend's argument list and invoke PostgresMain()
   *
   * returns:
   *		Doesn't return at all.
   */
  static void
  BackendRun(Port *port)
  {
  	/*
  	 * Make sure we aren't in PostmasterContext anymore.  (We can't delete it
  	 * just yet, though, because InitPostgres will need the HBA data.)
  	 */
  	MemoryContextSwitchTo(TopMemoryContext);
  
  	PostgresMain(port->database_name, port->user_name);
  }
  
  
  #ifdef EXEC_BACKEND
  
  /*
   * postmaster_forkexec -- fork and exec a postmaster subprocess
   *
   * The caller must have set up the argv array already, except for argv[2]
   * which will be filled with the name of the temp variable file.
   *
   * Returns the child process PID, or -1 on fork failure (a suitable error
   * message has been logged on failure).
   *
   * All uses of this routine will dispatch to SubPostmasterMain in the
   * child process.
   */
  pid_t
  postmaster_forkexec(int argc, char *argv[])
  {
  	Port		port;
  
  	/* This entry point passes dummy values for the Port variables */
  	memset(&port, 0, sizeof(port));
  	return internal_forkexec(argc, argv, &port);
  }
  
  /*
   * backend_forkexec -- fork/exec off a backend process
   *
   * Some operating systems (WIN32) don't have fork() so we have to simulate
   * it by storing parameters that need to be passed to the child and
   * then create a new child process.
   *
   * returns the pid of the fork/exec'd process, or -1 on failure
   */
  static pid_t
  backend_forkexec(Port *port)
  {
  	char	   *av[4];
  	int			ac = 0;
  
  	av[ac++] = "postgres";
  	av[ac++] = "--forkbackend";
  	av[ac++] = NULL;			/* filled in by internal_forkexec */
  
  	av[ac] = NULL;
  	Assert(ac < lengthof(av));
  
  	return internal_forkexec(ac, av, port);
  }
  
  #ifndef WIN32
  
  /*
   * internal_forkexec non-win32 implementation
   *
   * - writes out backend variables to the parameter file
   * - fork():s, and then exec():s the child process
   */
  static pid_t
  internal_forkexec(int argc, char *argv[], Port *port)
  {
  	static unsigned long tmpBackendFileNum = 0;
  	pid_t		pid;
  	char		tmpfilename[MAXPGPATH];
  	BackendParameters param;
  	FILE	   *fp;
  
  	if (!save_backend_variables(&param, port))
  		return -1;				/* log made by save_backend_variables */
  
  	/* Calculate name for temp file */
  	snprintf(tmpfilename, MAXPGPATH, "%s/%s.backend_var.%d.%lu",
  			 PG_TEMP_FILES_DIR, PG_TEMP_FILE_PREFIX,
  			 MyProcPid, ++tmpBackendFileNum);
  
  	/* Open file */
  	fp = AllocateFile(tmpfilename, PG_BINARY_W);
  	if (!fp)
  	{
  		/*
  		 * As in OpenTemporaryFileInTablespace, try to make the temp-file
  		 * directory, ignoring errors.
  		 */
  		(void) MakePGDirectory(PG_TEMP_FILES_DIR);
  
  		fp = AllocateFile(tmpfilename, PG_BINARY_W);
  		if (!fp)
  		{
  			ereport(LOG,
  					(errcode_for_file_access(),
  					 errmsg("could not create file \"%s\": %m",
  							tmpfilename)));
  			return -1;
  		}
  	}
  
  	if (fwrite(&param, sizeof(param), 1, fp) != 1)
  	{
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not write to file \"%s\": %m", tmpfilename)));
  		FreeFile(fp);
  		return -1;
  	}
  
  	/* Release file */
  	if (FreeFile(fp))
  	{
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not write to file \"%s\": %m", tmpfilename)));
  		return -1;
  	}
  
  	/* Make sure caller set up argv properly */
  	Assert(argc >= 3);
  	Assert(argv[argc] == NULL);
  	Assert(strncmp(argv[1], "--fork", 6) == 0);
  	Assert(argv[2] == NULL);
  
  	/* Insert temp file name after --fork argument */
  	argv[2] = tmpfilename;
  
  	/* Fire off execv in child */
  	if ((pid = fork_process()) == 0)
  	{
  		if (execv(postgres_exec_path, argv) < 0)
  		{
  			ereport(LOG,
  					(errmsg("could not execute server process \"%s\": %m",
  							postgres_exec_path)));
  			/* We're already in the child process here, can't return */
  			exit(1);
  		}
  	}
  
  	return pid;					/* Parent returns pid, or -1 on fork failure */
  }
  #else							/* WIN32 */
  
  /*
   * internal_forkexec win32 implementation
   *
   * - starts backend using CreateProcess(), in suspended state
   * - writes out backend variables to the parameter file
   *	- during this, duplicates handles and sockets required for
   *	  inheritance into the new process
   * - resumes execution of the new process once the backend parameter
   *	 file is complete.
   */
  static pid_t
  internal_forkexec(int argc, char *argv[], Port *port)
  {
  	int			retry_count = 0;
  	STARTUPINFO si;
  	PROCESS_INFORMATION pi;
  	int			i;
  	int			j;
  	char		cmdLine[MAXPGPATH * 2];
  	HANDLE		paramHandle;
  	BackendParameters *param;
  	SECURITY_ATTRIBUTES sa;
  	char		paramHandleStr[32];
  	win32_deadchild_waitinfo *childinfo;
  
  	/* Make sure caller set up argv properly */
  	Assert(argc >= 3);
  	Assert(argv[argc] == NULL);
  	Assert(strncmp(argv[1], "--fork", 6) == 0);
  	Assert(argv[2] == NULL);
  
  	/* Resume here if we need to retry */
  retry:
  
  	/* Set up shared memory for parameter passing */
  	ZeroMemory(&sa, sizeof(sa));
  	sa.nLength = sizeof(sa);
  	sa.bInheritHandle = TRUE;
  	paramHandle = CreateFileMapping(INVALID_HANDLE_VALUE,
  									&sa,
  									PAGE_READWRITE,
  									0,
  									sizeof(BackendParameters),
  									NULL);
  	if (paramHandle == INVALID_HANDLE_VALUE)
  	{
  		ereport(LOG,
  				(errmsg("could not create backend parameter file mapping: error code %lu",
  						GetLastError())));
  		return -1;
  	}
  
  	param = MapViewOfFile(paramHandle, FILE_MAP_WRITE, 0, 0, sizeof(BackendParameters));
  	if (!param)
  	{
  		ereport(LOG,
  				(errmsg("could not map backend parameter memory: error code %lu",
  						GetLastError())));
  		CloseHandle(paramHandle);
  		return -1;
  	}
  
  	/* Insert temp file name after --fork argument */
  #ifdef _WIN64
  	sprintf(paramHandleStr, "%llu", (LONG_PTR) paramHandle);
  #else
  	sprintf(paramHandleStr, "%lu", (DWORD) paramHandle);
  #endif
  	argv[2] = paramHandleStr;
  
  	/* Format the cmd line */
  	cmdLine[sizeof(cmdLine) - 1] = '\0';
  	cmdLine[sizeof(cmdLine) - 2] = '\0';
  	snprintf(cmdLine, sizeof(cmdLine) - 1, "\"%s\"", postgres_exec_path);
  	i = 0;
  	while (argv[++i] != NULL)
  	{
  		j = strlen(cmdLine);
  		snprintf(cmdLine + j, sizeof(cmdLine) - 1 - j, " \"%s\"", argv[i]);
  	}
  	if (cmdLine[sizeof(cmdLine) - 2] != '\0')
  	{
  		ereport(LOG,
  				(errmsg("subprocess command line too long")));
  		UnmapViewOfFile(param);
  		CloseHandle(paramHandle);
  		return -1;
  	}
  
  	memset(&pi, 0, sizeof(pi));
  	memset(&si, 0, sizeof(si));
  	si.cb = sizeof(si);
  
  	/*
  	 * Create the subprocess in a suspended state. This will be resumed later,
  	 * once we have written out the parameter file.
  	 */
  	if (!CreateProcess(NULL, cmdLine, NULL, NULL, TRUE, CREATE_SUSPENDED,
  					   NULL, NULL, &si, &pi))
  	{
  		ereport(LOG,
  				(errmsg("CreateProcess() call failed: %m (error code %lu)",
  						GetLastError())));
  		UnmapViewOfFile(param);
  		CloseHandle(paramHandle);
  		return -1;
  	}
  
  	if (!save_backend_variables(param, port, pi.hProcess, pi.dwProcessId))
  	{
  		/*
  		 * log made by save_backend_variables, but we have to clean up the
  		 * mess with the half-started process
  		 */
  		if (!TerminateProcess(pi.hProcess, 255))
  			ereport(LOG,
  					(errmsg_internal("could not terminate unstarted process: error code %lu",
  									 GetLastError())));
  		CloseHandle(pi.hProcess);
  		CloseHandle(pi.hThread);
  		UnmapViewOfFile(param);
  		CloseHandle(paramHandle);
  		return -1;				/* log made by save_backend_variables */
  	}
  
  	/* Drop the parameter shared memory that is now inherited to the backend */
  	if (!UnmapViewOfFile(param))
  		ereport(LOG,
  				(errmsg("could not unmap view of backend parameter file: error code %lu",
  						GetLastError())));
  	if (!CloseHandle(paramHandle))
  		ereport(LOG,
  				(errmsg("could not close handle to backend parameter file: error code %lu",
  						GetLastError())));
  
  	/*
  	 * Reserve the memory region used by our main shared memory segment before
  	 * we resume the child process.  Normally this should succeed, but if ASLR
  	 * is active then it might sometimes fail due to the stack or heap having
  	 * gotten mapped into that range.  In that case, just terminate the
  	 * process and retry.
  	 */
  	if (!pgwin32_ReserveSharedMemoryRegion(pi.hProcess))
  	{
  		/* pgwin32_ReserveSharedMemoryRegion already made a log entry */
  		if (!TerminateProcess(pi.hProcess, 255))
  			ereport(LOG,
  					(errmsg_internal("could not terminate process that failed to reserve memory: error code %lu",
  									 GetLastError())));
  		CloseHandle(pi.hProcess);
  		CloseHandle(pi.hThread);
  		if (++retry_count < 100)
  			goto retry;
  		ereport(LOG,
  				(errmsg("giving up after too many tries to reserve shared memory"),
  				 errhint("This might be caused by ASLR or antivirus software.")));
  		return -1;
  	}
  
  	/*
  	 * Now that the backend variables are written out, we start the child
  	 * thread so it can start initializing while we set up the rest of the
  	 * parent state.
  	 */
  	if (ResumeThread(pi.hThread) == -1)
  	{
  		if (!TerminateProcess(pi.hProcess, 255))
  		{
  			ereport(LOG,
  					(errmsg_internal("could not terminate unstartable process: error code %lu",
  									 GetLastError())));
  			CloseHandle(pi.hProcess);
  			CloseHandle(pi.hThread);
  			return -1;
  		}
  		CloseHandle(pi.hProcess);
  		CloseHandle(pi.hThread);
  		ereport(LOG,
  				(errmsg_internal("could not resume thread of unstarted process: error code %lu",
  								 GetLastError())));
  		return -1;
  	}
  
  	/*
  	 * Queue a waiter to signal when this child dies. The wait will be handled
  	 * automatically by an operating system thread pool.
  	 *
  	 * Note: use malloc instead of palloc, since it needs to be thread-safe.
  	 * Struct will be free():d from the callback function that runs on a
  	 * different thread.
  	 */
  	childinfo = malloc(sizeof(win32_deadchild_waitinfo));
  	if (!childinfo)
  		ereport(FATAL,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  
  	childinfo->procHandle = pi.hProcess;
  	childinfo->procId = pi.dwProcessId;
  
  	if (!RegisterWaitForSingleObject(&childinfo->waitHandle,
  									 pi.hProcess,
  									 pgwin32_deadchild_callback,
  									 childinfo,
  									 INFINITE,
  									 WT_EXECUTEONLYONCE | WT_EXECUTEINWAITTHREAD))
  		ereport(FATAL,
  				(errmsg_internal("could not register process for wait: error code %lu",
  								 GetLastError())));
  
  	/* Don't close pi.hProcess here - the wait thread needs access to it */
  
  	CloseHandle(pi.hThread);
  
  	return pi.dwProcessId;
  }
  #endif							/* WIN32 */
  
  
  /*
   * SubPostmasterMain -- Get the fork/exec'd process into a state equivalent
   *			to what it would be if we'd simply forked on Unix, and then
   *			dispatch to the appropriate place.
   *
   * The first two command line arguments are expected to be "--forkFOO"
   * (where FOO indicates which postmaster child we are to become), and
   * the name of a variables file that we can read to load data that would
   * have been inherited by fork() on Unix.  Remaining arguments go to the
   * subprocess FooMain() routine.
   */
  void
  SubPostmasterMain(int argc, char *argv[])
  {
  	Port		port;
  
  	/* In EXEC_BACKEND case we will not have inherited these settings */
  	IsPostmasterEnvironment = true;
  	whereToSendOutput = DestNone;
  
  	/* Setup essential subsystems (to ensure elog() behaves sanely) */
  	InitializeGUCOptions();
  
  	/* Check we got appropriate args */
  	if (argc < 3)
  		elog(FATAL, "invalid subpostmaster invocation");
  
  	/* Read in the variables file */
  	memset(&port, 0, sizeof(Port));
  	read_backend_variables(argv[2], &port);
  
  	/* Close the postmaster's sockets (as soon as we know them) */
  	ClosePostmasterPorts(strcmp(argv[1], "--forklog") == 0);
  
  	/* Setup as postmaster child */
  	InitPostmasterChild();
  
  	/*
  	 * If appropriate, physically re-attach to shared memory segment. We want
  	 * to do this before going any further to ensure that we can attach at the
  	 * same address the postmaster used.  On the other hand, if we choose not
  	 * to re-attach, we may have other cleanup to do.
  	 *
  	 * If testing EXEC_BACKEND on Linux, you should run this as root before
  	 * starting the postmaster:
  	 *
  	 * echo 0 >/proc/sys/kernel/randomize_va_space
  	 *
  	 * This prevents using randomized stack and code addresses that cause the
  	 * child process's memory map to be different from the parent's, making it
  	 * sometimes impossible to attach to shared memory at the desired address.
  	 * Return the setting to its old value (usually '1' or '2') when finished.
  	 */
  	if (strcmp(argv[1], "--forkbackend") == 0 ||
  		strcmp(argv[1], "--forkavlauncher") == 0 ||
  		strcmp(argv[1], "--forkavworker") == 0 ||
  		strcmp(argv[1], "--forkaux") == 0 ||
  		strncmp(argv[1], "--forkbgworker=", 15) == 0)
  		PGSharedMemoryReAttach();
  	else
  		PGSharedMemoryNoReAttach();
  
  	/* autovacuum needs this set before calling InitProcess */
  	if (strcmp(argv[1], "--forkavlauncher") == 0)
  		AutovacuumLauncherIAm();
  	if (strcmp(argv[1], "--forkavworker") == 0)
  		AutovacuumWorkerIAm();
  
  	/* Read in remaining GUC variables */
  	read_nondefault_variables();
  
  	/*
  	 * Check that the data directory looks valid, which will also check the
  	 * privileges on the data directory and update our umask and file/group
  	 * variables for creating files later.  Note: this should really be done
  	 * before we create any files or directories.
  	 */
  	checkDataDir();
  
  	/*
  	 * (re-)read control file, as it contains config. The postmaster will
  	 * already have read this, but this process doesn't know about that.
  	 */
  	LocalProcessControlFile(false);
  
  	/*
  	 * Reload any libraries that were preloaded by the postmaster.  Since we
  	 * exec'd this process, those libraries didn't come along with us; but we
  	 * should load them into all child processes to be consistent with the
  	 * non-EXEC_BACKEND behavior.
  	 */
  	process_shared_preload_libraries();
  
  	/* Run backend or appropriate child */
  	if (strcmp(argv[1], "--forkbackend") == 0)
  	{
  		Assert(argc == 3);		/* shouldn't be any more args */
  
  		/*
  		 * Need to reinitialize the SSL library in the backend, since the
  		 * context structures contain function pointers and cannot be passed
  		 * through the parameter file.
  		 *
  		 * If for some reason reload fails (maybe the user installed broken
  		 * key files), soldier on without SSL; that's better than all
  		 * connections becoming impossible.
  		 *
  		 * XXX should we do this in all child processes?  For the moment it's
  		 * enough to do it in backend children.
  		 */
  #ifdef USE_SSL
  		if (EnableSSL)
  		{
  			if (secure_initialize(false) == 0)
  				LoadedSSL = true;
  			else
  				ereport(LOG,
  						(errmsg("SSL configuration could not be loaded in child process")));
  		}
  #endif
  
  		/*
  		 * Perform additional initialization and collect startup packet.
  		 *
  		 * We want to do this before InitProcess() for a couple of reasons: 1.
  		 * so that we aren't eating up a PGPROC slot while waiting on the
  		 * client. 2. so that if InitProcess() fails due to being out of
  		 * PGPROC slots, we have already initialized libpq and are able to
  		 * report the error to the client.
  		 */
  		BackendInitialize(&port);
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores();
  
  		/* And run the backend */
  		BackendRun(&port);		/* does not return */
  	}
  	if (strcmp(argv[1], "--forkaux") == 0)
  	{
  		AuxProcType auxtype;
  
  		Assert(argc == 4);
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitAuxiliaryProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores();
  
  		auxtype = atoi(argv[3]);
  		AuxiliaryProcessMain(auxtype);	/* does not return */
  	}
  	if (strcmp(argv[1], "--forkavlauncher") == 0)
  	{
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores();
  
  		AutoVacLauncherMain(argc - 2, argv + 2);	/* does not return */
  	}
  	if (strcmp(argv[1], "--forkavworker") == 0)
  	{
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores();
  
  		AutoVacWorkerMain(argc - 2, argv + 2);	/* does not return */
  	}
  	if (strncmp(argv[1], "--forkbgworker=", 15) == 0)
  	{
  		int			shmem_slot;
  
  		/* do this as early as possible; in particular, before InitProcess() */
  		IsBackgroundWorker = true;
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores();
  
  		/* Fetch MyBgworkerEntry from shared memory */
  		shmem_slot = atoi(argv[1] + 15);
  		MyBgworkerEntry = BackgroundWorkerEntry(shmem_slot);
  
  		StartBackgroundWorker();
  	}
  	if (strcmp(argv[1], "--forklog") == 0)
  	{
  		/* Do not want to attach to shared memory */
  
  		SysLoggerMain(argc, argv);	/* does not return */
  	}
  
  	abort();					/* shouldn't get here */
  }
  #endif							/* EXEC_BACKEND */
  
  
  /*
   * ExitPostmaster -- cleanup
   *
   * Do NOT call exit() directly --- always go through here!
   */
  static void
  ExitPostmaster(int status)
  {
  #ifdef HAVE_PTHREAD_IS_THREADED_NP
  
  	/*
  	 * There is no known cause for a postmaster to become multithreaded after
  	 * startup.  Recheck to account for the possibility of unknown causes.
  	 * This message uses LOG level, because an unclean shutdown at this point
  	 * would usually not look much different from a clean shutdown.
  	 */
  	if (pthread_is_threaded_np() != 0)
  		ereport(LOG,
  				(errcode(ERRCODE_INTERNAL_ERROR),
  				 errmsg_internal("postmaster became multithreaded"),
  				 errdetail("Please report this to <%s>.", PACKAGE_BUGREPORT)));
  #endif
  
  	/* should cleanup shared memory and kill all backends */
  
  	/*
  	 * Not sure of the semantics here.  When the Postmaster dies, should the
  	 * backends all be killed? probably not.
  	 *
  	 * MUST		-- vadim 05-10-1999
  	 */
  
  	proc_exit(status);
  }
  
  /*
   * sigusr1_handler - handle signal conditions from child processes
   */
  static void
  sigusr1_handler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	/*
  	 * We rely on the signal mechanism to have blocked all signals ... except
  	 * on Windows, which lacks sigaction(), so we have to do it manually.
  	 */
  #ifdef WIN32
  	PG_SETMASK(&BlockSig);
  #endif
  
  	/*
  	 * RECOVERY_STARTED and BEGIN_HOT_STANDBY signals are ignored in
  	 * unexpected states. If the startup process quickly starts up, completes
  	 * recovery, exits, we might process the death of the startup process
  	 * first. We don't want to go back to recovery in that case.
  	 */
  	if (CheckPostmasterSignal(PMSIGNAL_RECOVERY_STARTED) &&
  		pmState == PM_STARTUP && Shutdown == NoShutdown)
  	{
  		/* WAL redo has started. We're out of reinitialization. */
  		FatalError = false;
  		AbortStartTime = 0;
  
  		/*
  		 * Start the archiver if we're responsible for (re-)archiving received
  		 * files.
  		 */
  		Assert(PgArchPID == 0);
  		if (XLogArchivingAlways())
  			PgArchPID = StartArchiver();
  
  		/*
  		 * If we aren't planning to enter hot standby mode later, treat
  		 * RECOVERY_STARTED as meaning we're out of startup, and report status
  		 * accordingly.
  		 */
  		if (!EnableHotStandby)
  		{
  			AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_STANDBY);
  #ifdef USE_SYSTEMD
  			sd_notify(0, "READY=1");
  #endif
  		}
  
  		pmState = PM_RECOVERY;
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) &&
  		pmState == PM_RECOVERY && Shutdown == NoShutdown)
  	{
  		ereport(LOG,
  				(errmsg("database system is ready to accept read-only connections")));
  
  		/* Report status */
  		AddToDataDirLockFile(LOCK_FILE_LINE_PM_STATUS, PM_STATUS_READY);
  #ifdef USE_SYSTEMD
  		sd_notify(0, "READY=1");
  #endif
  
  		pmState = PM_HOT_STANDBY;
  		connsAllowed = true;
  
  		/* Some workers may be scheduled to start now */
  		StartWorkerNeeded = true;
  	}
  
  	/* Process background worker state changes. */
  	if (CheckPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE))
  	{
  		/* Accept new worker requests only if not stopping. */
  		BackgroundWorkerStateChange(pmState < PM_STOP_BACKENDS);
  		StartWorkerNeeded = true;
  	}
  
  	if (StartWorkerNeeded || HaveCrashedWorker)
  		maybe_start_bgworkers();
  
  	/* Tell syslogger to rotate logfile if requested */
  	if (SysLoggerPID != 0)
  	{
  		if (CheckLogrotateSignal())
  		{
  			signal_child(SysLoggerPID, SIGUSR1);
  			RemoveLogrotateSignalFiles();
  		}
  		else if (CheckPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE))
  		{
  			signal_child(SysLoggerPID, SIGUSR1);
  		}
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER) &&
  		Shutdown <= SmartShutdown && pmState < PM_STOP_BACKENDS)
  	{
  		/*
  		 * Start one iteration of the autovacuum daemon, even if autovacuuming
  		 * is nominally not enabled.  This is so we can have an active defense
  		 * against transaction ID wraparound.  We set a flag for the main loop
  		 * to do it rather than trying to do it here --- this is because the
  		 * autovac process itself may send the signal, and we want to handle
  		 * that by launching another iteration as soon as the current one
  		 * completes.
  		 */
  		start_autovac_launcher = true;
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_WORKER) &&
  		Shutdown <= SmartShutdown && pmState < PM_STOP_BACKENDS)
  	{
  		/* The autovacuum launcher wants us to start a worker process. */
  		StartAutovacuumWorker();
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_START_WALRECEIVER))
  	{
  		/* Startup Process wants us to start the walreceiver process. */
  		/* Start immediately if possible, else remember request for later. */
  		WalReceiverRequested = true;
  		MaybeStartWalReceiver();
  	}
  
  	/*
  	 * Try to advance postmaster's state machine, if a child requests it.
  	 *
  	 * Be careful about the order of this action relative to sigusr1_handler's
  	 * other actions.  Generally, this should be after other actions, in case
  	 * they have effects PostmasterStateMachine would need to know about.
  	 * However, we should do it before the CheckPromoteSignal step, which
  	 * cannot have any (immediate) effect on the state machine, but does
  	 * depend on what state we're in now.
  	 */
  	if (CheckPostmasterSignal(PMSIGNAL_ADVANCE_STATE_MACHINE))
  	{
  		PostmasterStateMachine();
  	}
  
  	if (StartupPID != 0 &&
  		(pmState == PM_STARTUP || pmState == PM_RECOVERY ||
  		 pmState == PM_HOT_STANDBY) &&
  		CheckPromoteSignal())
  	{
  		/*
  		 * Tell startup process to finish recovery.
  		 *
  		 * Leave the promote signal file in place and let the Startup process
  		 * do the unlink.
  		 */
  		signal_child(StartupPID, SIGUSR2);
  	}
  
  #ifdef WIN32
  	PG_SETMASK(&UnBlockSig);
  #endif
  
  	errno = save_errno;
  }
  
  /*
   * SIGTERM while processing startup packet.
   *
   * Running proc_exit() from a signal handler would be quite unsafe.
   * However, since we have not yet touched shared memory, we can just
   * pull the plug and exit without running any atexit handlers.
   *
   * One might be tempted to try to send a message, or log one, indicating
   * why we are disconnecting.  However, that would be quite unsafe in itself.
   * Also, it seems undesirable to provide clues about the database's state
   * to a client that has not yet completed authentication, or even sent us
   * a startup packet.
   */
  static void
  process_startup_packet_die(SIGNAL_ARGS)
  {
  	_exit(1);
  }
  
  /*
   * Dummy signal handler
   *
   * We use this for signals that we don't actually use in the postmaster,
   * but we do use in backends.  If we were to SIG_IGN such signals in the
   * postmaster, then a newly started backend might drop a signal that arrives
   * before it's able to reconfigure its signal processing.  (See notes in
   * tcop/postgres.c.)
   */
  static void
  dummy_handler(SIGNAL_ARGS)
  {
  }
  
  /*
   * Timeout while processing startup packet.
   * As for process_startup_packet_die(), we exit via _exit(1).
   */
  static void
  StartupPacketTimeoutHandler(void)
  {
  	_exit(1);
  }
  
  
  /*
   * Generate a random cancel key.
   */
  static bool
  RandomCancelKey(int32 *cancel_key)
  {
  	return pg_strong_random(cancel_key, sizeof(int32));
  }
  
  /*
   * Count up number of child processes of specified types (dead_end children
   * are always excluded).
   */
  static int
  CountChildren(int target)
  {
  	dlist_iter	iter;
  	int			cnt = 0;
  
  	dlist_foreach(iter, &BackendList)
  	{
  		Backend    *bp = dlist_container(Backend, elem, iter.cur);
  
  		if (bp->dead_end)
  			continue;
  
  		/*
  		 * Since target == BACKEND_TYPE_ALL is the most common case, we test
  		 * it first and avoid touching shared memory for every child.
  		 */
  		if (target != BACKEND_TYPE_ALL)
  		{
  			/*
  			 * Assign bkend_type for any recently announced WAL Sender
  			 * processes.
  			 */
  			if (bp->bkend_type == BACKEND_TYPE_NORMAL &&
  				IsPostmasterChildWalSender(bp->child_slot))
  				bp->bkend_type = BACKEND_TYPE_WALSND;
  
  			if (!(target & bp->bkend_type))
  				continue;
  		}
  
  		cnt++;
  	}
  	return cnt;
  }
  
  
  /*
   * StartChildProcess -- start an auxiliary process for the postmaster
   *
   * "type" determines what kind of child will be started.  All child types
   * initially go to AuxiliaryProcessMain, which will handle common setup.
   *
   * Return value of StartChildProcess is subprocess' PID, or 0 if failed
   * to start subprocess.
   */
  static pid_t
  StartChildProcess(AuxProcType type)
  {
  	pid_t		pid;
  
  #ifdef EXEC_BACKEND
  	{
  		char	   *av[10];
  		int			ac = 0;
  		char		typebuf[32];
  
  		/*
  		 * Set up command-line arguments for subprocess
  		 */
  		av[ac++] = "postgres";
  		av[ac++] = "--forkaux";
  		av[ac++] = NULL;		/* filled in by postmaster_forkexec */
  
  		snprintf(typebuf, sizeof(typebuf), "%d", type);
  		av[ac++] = typebuf;
  
  		av[ac] = NULL;
  		Assert(ac < lengthof(av));
  
  		pid = postmaster_forkexec(ac, av);
  	}
  #else							/* !EXEC_BACKEND */
  	pid = fork_process();
  
  	if (pid == 0)				/* child */
  	{
  		InitPostmasterChild();
  
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Release postmaster's working memory context */
  		MemoryContextSwitchTo(TopMemoryContext);
  		MemoryContextDelete(PostmasterContext);
  		PostmasterContext = NULL;
  
  		AuxiliaryProcessMain(type); /* does not return */
  	}
  #endif							/* EXEC_BACKEND */
  
  	if (pid < 0)
  	{
  		/* in parent, fork failed */
  		int			save_errno = errno;
  
  		errno = save_errno;
  		switch (type)
  		{
  			case StartupProcess:
  				ereport(LOG,
  						(errmsg("could not fork startup process: %m")));
  				break;
  			case ArchiverProcess:
  				ereport(LOG,
  						(errmsg("could not fork archiver process: %m")));
  				break;
  			case BgWriterProcess:
  				ereport(LOG,
  						(errmsg("could not fork background writer process: %m")));
  				break;
  			case CheckpointerProcess:
  				ereport(LOG,
  						(errmsg("could not fork checkpointer process: %m")));
  				break;
  			case WalWriterProcess:
  				ereport(LOG,
  						(errmsg("could not fork WAL writer process: %m")));
  				break;
  			case WalReceiverProcess:
  				ereport(LOG,
  						(errmsg("could not fork WAL receiver process: %m")));
  				break;
  			default:
  				ereport(LOG,
  						(errmsg("could not fork process: %m")));
  				break;
  		}
  
  		/*
  		 * fork failure is fatal during startup, but there's no need to choke
  		 * immediately if starting other child types fails.
  		 */
  		if (type == StartupProcess)
  			ExitPostmaster(1);
  		return 0;
  	}
  
  	/*
  	 * in parent, successful fork
  	 */
  	return pid;
  }
  
  /*
   * StartAutovacuumWorker
   *		Start an autovac worker process.
   *
   * This function is here because it enters the resulting PID into the
   * postmaster's private backends list.
   *
   * NB -- this code very roughly matches BackendStartup.
   */
  static void
  StartAutovacuumWorker(void)
  {
  	Backend    *bn;
  
  	/*
  	 * If not in condition to run a process, don't try, but handle it like a
  	 * fork failure.  This does not normally happen, since the signal is only
  	 * supposed to be sent by autovacuum launcher when it's OK to do it, but
  	 * we have to check to avoid race-condition problems during DB state
  	 * changes.
  	 */
  	if (canAcceptConnections(BACKEND_TYPE_AUTOVAC) == CAC_OK)
  	{
  		/*
  		 * Compute the cancel key that will be assigned to this session. We
  		 * probably don't need cancel keys for autovac workers, but we'd
  		 * better have something random in the field to prevent unfriendly
  		 * people from sending cancels to them.
  		 */
  		if (!RandomCancelKey(&MyCancelKey))
  		{
  			ereport(LOG,
  					(errcode(ERRCODE_INTERNAL_ERROR),
  					 errmsg("could not generate random cancel key")));
  			return;
  		}
  
  		bn = (Backend *) malloc(sizeof(Backend));
  		if (bn)
  		{
  			bn->cancel_key = MyCancelKey;
  
  			/* Autovac workers are not dead_end and need a child slot */
  			bn->dead_end = false;
  			bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
  			bn->bgworker_notify = false;
  
  			bn->pid = StartAutoVacWorker();
  			if (bn->pid > 0)
  			{
  				bn->bkend_type = BACKEND_TYPE_AUTOVAC;
  				dlist_push_head(&BackendList, &bn->elem);
  #ifdef EXEC_BACKEND
  				ShmemBackendArrayAdd(bn);
  #endif
  				/* all OK */
  				return;
  			}
  
  			/*
  			 * fork failed, fall through to report -- actual error message was
  			 * logged by StartAutoVacWorker
  			 */
  			(void) ReleasePostmasterChildSlot(bn->child_slot);
  			free(bn);
  		}
  		else
  			ereport(LOG,
  					(errcode(ERRCODE_OUT_OF_MEMORY),
  					 errmsg("out of memory")));
  	}
  
  	/*
  	 * Report the failure to the launcher, if it's running.  (If it's not, we
  	 * might not even be connected to shared memory, so don't try to call
  	 * AutoVacWorkerFailed.)  Note that we also need to signal it so that it
  	 * responds to the condition, but we don't do that here, instead waiting
  	 * for ServerLoop to do it.  This way we avoid a ping-pong signaling in
  	 * quick succession between the autovac launcher and postmaster in case
  	 * things get ugly.
  	 */
  	if (AutoVacPID != 0)
  	{
  		AutoVacWorkerFailed();
  		avlauncher_needs_signal = true;
  	}
  }
  
  /*
   * MaybeStartWalReceiver
   *		Start the WAL receiver process, if not running and our state allows.
   *
   * Note: if WalReceiverPID is already nonzero, it might seem that we should
   * clear WalReceiverRequested.  However, there's a race condition if the
   * walreceiver terminates and the startup process immediately requests a new
   * one: it's quite possible to get the signal for the request before reaping
   * the dead walreceiver process.  Better to risk launching an extra
   * walreceiver than to miss launching one we need.  (The walreceiver code
   * has logic to recognize that it should go away if not needed.)
   */
  static void
  MaybeStartWalReceiver(void)
  {
  	if (WalReceiverPID == 0 &&
  		(pmState == PM_STARTUP || pmState == PM_RECOVERY ||
  		 pmState == PM_HOT_STANDBY) &&
  		Shutdown <= SmartShutdown)
  	{
  		WalReceiverPID = StartWalReceiver();
  		if (WalReceiverPID != 0)
  			WalReceiverRequested = false;
  		/* else leave the flag set, so we'll try again later */
  	}
  }
  
  
  /*
   * Create the opts file
   */
  static bool
  CreateOptsFile(int argc, char *argv[], char *fullprogname)
  {
  	FILE	   *fp;
  	int			i;
  
  #define OPTS_FILE	"postmaster.opts"
  
  	if ((fp = fopen(OPTS_FILE, "w")) == NULL)
  	{
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not create file \"%s\": %m", OPTS_FILE)));
  		return false;
  	}
  
  	fprintf(fp, "%s", fullprogname);
  	for (i = 1; i < argc; i++)
  		fprintf(fp, " \"%s\"", argv[i]);
  	fputs("\n", fp);
  
  	if (fclose(fp))
  	{
  		ereport(LOG,
  				(errcode_for_file_access(),
  				 errmsg("could not write file \"%s\": %m", OPTS_FILE)));
  		return false;
  	}
  
  	return true;
  }
  
  
  /*
   * MaxLivePostmasterChildren
   *
   * This reports the number of entries needed in per-child-process arrays
   * (the PMChildFlags array, and if EXEC_BACKEND the ShmemBackendArray).
   * These arrays include regular backends, autovac workers, walsenders
   * and background workers, but not special children nor dead_end children.
   * This allows the arrays to have a fixed maximum size, to wit the same
   * too-many-children limit enforced by canAcceptConnections().  The exact value
   * isn't too critical as long as it's more than MaxBackends.
   */
  int
  MaxLivePostmasterChildren(void)
  {
  	return 2 * (MaxConnections + autovacuum_max_workers + 1 +
  				max_wal_senders + max_worker_processes);
  }
  
  /*
   * Connect background worker to a database.
   */
  void
  BackgroundWorkerInitializeConnection(const char *dbname, const char *username, uint32 flags)
  {
  	BackgroundWorker *worker = MyBgworkerEntry;
  
  	/* XXX is this the right errcode? */
  	if (!(worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION))
  		ereport(FATAL,
  				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
  				 errmsg("database connection requirement not indicated during registration")));
  
  	InitPostgres(dbname, InvalidOid, username, InvalidOid, NULL, (flags & BGWORKER_BYPASS_ALLOWCONN) != 0);
  
  	/* it had better not gotten out of "init" mode yet */
  	if (!IsInitProcessingMode())
  		ereport(ERROR,
  				(errmsg("invalid processing mode in background worker")));
  	SetProcessingMode(NormalProcessing);
  }
  
  /*
   * Connect background worker to a database using OIDs.
   */
  void
  BackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid, uint32 flags)
  {
  	BackgroundWorker *worker = MyBgworkerEntry;
  
  	/* XXX is this the right errcode? */
  	if (!(worker->bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION))
  		ereport(FATAL,
  				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
  				 errmsg("database connection requirement not indicated during registration")));
  
  	InitPostgres(NULL, dboid, NULL, useroid, NULL, (flags & BGWORKER_BYPASS_ALLOWCONN) != 0);
  
  	/* it had better not gotten out of "init" mode yet */
  	if (!IsInitProcessingMode())
  		ereport(ERROR,
  				(errmsg("invalid processing mode in background worker")));
  	SetProcessingMode(NormalProcessing);
  }
  
  /*
   * Block/unblock signals in a background worker
   */
  void
  BackgroundWorkerBlockSignals(void)
  {
  	PG_SETMASK(&BlockSig);
  }
  
  void
  BackgroundWorkerUnblockSignals(void)
  {
  	PG_SETMASK(&UnBlockSig);
  }
  
  #ifdef EXEC_BACKEND
  static pid_t
  bgworker_forkexec(int shmem_slot)
  {
  	char	   *av[10];
  	int			ac = 0;
  	char		forkav[MAXPGPATH];
  
  	snprintf(forkav, MAXPGPATH, "--forkbgworker=%d", shmem_slot);
  
  	av[ac++] = "postgres";
  	av[ac++] = forkav;
  	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
  	av[ac] = NULL;
  
  	Assert(ac < lengthof(av));
  
  	return postmaster_forkexec(ac, av);
  }
  #endif
  
  /*
   * Start a new bgworker.
   * Starting time conditions must have been checked already.
   *
   * Returns true on success, false on failure.
   * In either case, update the RegisteredBgWorker's state appropriately.
   *
   * This code is heavily based on autovacuum.c, q.v.
   */
  static bool
  do_start_bgworker(RegisteredBgWorker *rw)
  {
  	pid_t		worker_pid;
  
  	Assert(rw->rw_pid == 0);
  
  	/*
  	 * Allocate and assign the Backend element.  Note we must do this before
  	 * forking, so that we can handle failures (out of memory or child-process
  	 * slots) cleanly.
  	 *
  	 * Treat failure as though the worker had crashed.  That way, the
  	 * postmaster will wait a bit before attempting to start it again; if we
  	 * tried again right away, most likely we'd find ourselves hitting the
  	 * same resource-exhaustion condition.
  	 */
  	if (!assign_backendlist_entry(rw))
  	{
  		rw->rw_crashed_at = GetCurrentTimestamp();
  		return false;
  	}
  
  	ereport(DEBUG1,
  			(errmsg_internal("starting background worker process \"%s\"",
  							 rw->rw_worker.bgw_name)));
  
  #ifdef EXEC_BACKEND
  	switch ((worker_pid = bgworker_forkexec(rw->rw_shmem_slot)))
  #else
  	switch ((worker_pid = fork_process()))
  #endif
  	{
  		case -1:
  			/* in postmaster, fork failed ... */
  			ereport(LOG,
  					(errmsg("could not fork worker process: %m")));
  			/* undo what assign_backendlist_entry did */
  			ReleasePostmasterChildSlot(rw->rw_child_slot);
  			rw->rw_child_slot = 0;
  			free(rw->rw_backend);
  			rw->rw_backend = NULL;
  			/* mark entry as crashed, so we'll try again later */
  			rw->rw_crashed_at = GetCurrentTimestamp();
  			break;
  
  #ifndef EXEC_BACKEND
  		case 0:
  			/* in postmaster child ... */
  			InitPostmasterChild();
  
  			/* Close the postmaster's sockets */
  			ClosePostmasterPorts(false);
  
  			/*
  			 * Before blowing away PostmasterContext, save this bgworker's
  			 * data where it can find it.
  			 */
  			MyBgworkerEntry = (BackgroundWorker *)
  				MemoryContextAlloc(TopMemoryContext, sizeof(BackgroundWorker));
  			memcpy(MyBgworkerEntry, &rw->rw_worker, sizeof(BackgroundWorker));
  
  			/* Release postmaster's working memory context */
  			MemoryContextSwitchTo(TopMemoryContext);
  			MemoryContextDelete(PostmasterContext);
  			PostmasterContext = NULL;
  
  			StartBackgroundWorker();
  
  			exit(1);			/* should not get here */
  			break;
  #endif
  		default:
  			/* in postmaster, fork successful ... */
  			rw->rw_pid = worker_pid;
  			rw->rw_backend->pid = rw->rw_pid;
  			ReportBackgroundWorkerPID(rw);
  			/* add new worker to lists of backends */
  			dlist_push_head(&BackendList, &rw->rw_backend->elem);
  #ifdef EXEC_BACKEND
  			ShmemBackendArrayAdd(rw->rw_backend);
  #endif
  			return true;
  	}
  
  	return false;
  }
  
  /*
   * Does the current postmaster state require starting a worker with the
   * specified start_time?
   */
  static bool
  bgworker_should_start_now(BgWorkerStartTime start_time)
  {
  	switch (pmState)
  	{
  		case PM_NO_CHILDREN:
  		case PM_WAIT_DEAD_END:
  		case PM_SHUTDOWN_2:
  		case PM_SHUTDOWN:
  		case PM_WAIT_BACKENDS:
  		case PM_STOP_BACKENDS:
  			break;
  
  		case PM_RUN:
  			if (start_time == BgWorkerStart_RecoveryFinished)
  				return true;
  			/* fall through */
  
  		case PM_HOT_STANDBY:
  			if (start_time == BgWorkerStart_ConsistentState)
  				return true;
  			/* fall through */
  
  		case PM_RECOVERY:
  		case PM_STARTUP:
  		case PM_INIT:
  			if (start_time == BgWorkerStart_PostmasterStart)
  				return true;
  			/* fall through */
  
  	}
  
  	return false;
  }
  
  /*
   * Allocate the Backend struct for a connected background worker, but don't
   * add it to the list of backends just yet.
   *
   * On failure, return false without changing any worker state.
   *
   * Some info from the Backend is copied into the passed rw.
   */
  static bool
  assign_backendlist_entry(RegisteredBgWorker *rw)
  {
  	Backend    *bn;
  
  	/*
  	 * Check that database state allows another connection.  Currently the
  	 * only possible failure is CAC_TOOMANY, so we just log an error message
  	 * based on that rather than checking the error code precisely.
  	 */
  	if (canAcceptConnections(BACKEND_TYPE_BGWORKER) != CAC_OK)
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
  				 errmsg("no slot available for new worker process")));
  		return false;
  	}
  
  	/*
  	 * Compute the cancel key that will be assigned to this session. We
  	 * probably don't need cancel keys for background workers, but we'd better
  	 * have something random in the field to prevent unfriendly people from
  	 * sending cancels to them.
  	 */
  	if (!RandomCancelKey(&MyCancelKey))
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_INTERNAL_ERROR),
  				 errmsg("could not generate random cancel key")));
  		return false;
  	}
  
  	bn = malloc(sizeof(Backend));
  	if (bn == NULL)
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  		return false;
  	}
  
  	bn->cancel_key = MyCancelKey;
  	bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
  	bn->bkend_type = BACKEND_TYPE_BGWORKER;
  	bn->dead_end = false;
  	bn->bgworker_notify = false;
  
  	rw->rw_backend = bn;
  	rw->rw_child_slot = bn->child_slot;
  
  	return true;
  }
  
  /*
   * If the time is right, start background worker(s).
   *
   * As a side effect, the bgworker control variables are set or reset
   * depending on whether more workers may need to be started.
   *
   * We limit the number of workers started per call, to avoid consuming the
   * postmaster's attention for too long when many such requests are pending.
   * As long as StartWorkerNeeded is true, ServerLoop will not block and will
   * call this function again after dealing with any other issues.
   */
  static void
  maybe_start_bgworkers(void)
  {
  #define MAX_BGWORKERS_TO_LAUNCH 100
  	int			num_launched = 0;
  	TimestampTz now = 0;
  	slist_mutable_iter iter;
  
  	/*
  	 * During crash recovery, we have no need to be called until the state
  	 * transition out of recovery.
  	 */
  	if (FatalError)
  	{
  		StartWorkerNeeded = false;
  		HaveCrashedWorker = false;
  		return;
  	}
  
  	/* Don't need to be called again unless we find a reason for it below */
  	StartWorkerNeeded = false;
  	HaveCrashedWorker = false;
  
  	slist_foreach_modify(iter, &BackgroundWorkerList)
  	{
  		RegisteredBgWorker *rw;
  
  		rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
  
  		/* ignore if already running */
  		if (rw->rw_pid != 0)
  			continue;
  
  		/* if marked for death, clean up and remove from list */
  		if (rw->rw_terminate)
  		{
  			ForgetBackgroundWorker(&iter);
  			continue;
  		}
  
  		/*
  		 * If this worker has crashed previously, maybe it needs to be
  		 * restarted (unless on registration it specified it doesn't want to
  		 * be restarted at all).  Check how long ago did a crash last happen.
  		 * If the last crash is too recent, don't start it right away; let it
  		 * be restarted once enough time has passed.
  		 */
  		if (rw->rw_crashed_at != 0)
  		{
  			if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
  			{
  				int			notify_pid;
  
  				notify_pid = rw->rw_worker.bgw_notify_pid;
  
  				ForgetBackgroundWorker(&iter);
  
  				/* Report worker is gone now. */
  				if (notify_pid != 0)
  					kill(notify_pid, SIGUSR1);
  
  				continue;
  			}
  
  			/* read system time only when needed */
  			if (now == 0)
  				now = GetCurrentTimestamp();
  
  			if (!TimestampDifferenceExceeds(rw->rw_crashed_at, now,
  											rw->rw_worker.bgw_restart_time * 1000))
  			{
  				/* Set flag to remember that we have workers to start later */
  				HaveCrashedWorker = true;
  				continue;
  			}
  		}
  
  		if (bgworker_should_start_now(rw->rw_worker.bgw_start_time))
  		{
  			/* reset crash time before trying to start worker */
  			rw->rw_crashed_at = 0;
  
  			/*
  			 * Try to start the worker.
  			 *
  			 * On failure, give up processing workers for now, but set
  			 * StartWorkerNeeded so we'll come back here on the next iteration
  			 * of ServerLoop to try again.  (We don't want to wait, because
  			 * there might be additional ready-to-run workers.)  We could set
  			 * HaveCrashedWorker as well, since this worker is now marked
  			 * crashed, but there's no need because the next run of this
  			 * function will do that.
  			 */
  			if (!do_start_bgworker(rw))
  			{
  				StartWorkerNeeded = true;
  				return;
  			}
  
  			/*
  			 * If we've launched as many workers as allowed, quit, but have
  			 * ServerLoop call us again to look for additional ready-to-run
  			 * workers.  There might not be any, but we'll find out the next
  			 * time we run.
  			 */
  			if (++num_launched >= MAX_BGWORKERS_TO_LAUNCH)
  			{
  				StartWorkerNeeded = true;
  				return;
  			}
  		}
  	}
  }
  
  /*
   * When a backend asks to be notified about worker state changes, we
   * set a flag in its backend entry.  The background worker machinery needs
   * to know when such backends exit.
   */
  bool
  PostmasterMarkPIDForWorkerNotify(int pid)
  {
  	dlist_iter	iter;
  	Backend    *bp;
  
  	dlist_foreach(iter, &BackendList)
  	{
  		bp = dlist_container(Backend, elem, iter.cur);
  		if (bp->pid == pid)
  		{
  			bp->bgworker_notify = true;
  			return true;
  		}
  	}
  	return false;
  }
  
  #ifdef EXEC_BACKEND
  
  /*
   * The following need to be available to the save/restore_backend_variables
   * functions.  They are marked NON_EXEC_STATIC in their home modules.
   */
  extern slock_t *ShmemLock;
  extern slock_t *ProcStructLock;
  extern PGPROC *AuxiliaryProcs;
  extern PMSignalData *PMSignalState;
  extern pg_time_t first_syslogger_file_time;
  
  #ifndef WIN32
  #define write_inheritable_socket(dest, src, childpid) ((*(dest) = (src)), true)
  #define read_inheritable_socket(dest, src) (*(dest) = *(src))
  #else
  static bool write_duplicated_handle(HANDLE *dest, HANDLE src, HANDLE child);
  static bool write_inheritable_socket(InheritableSocket *dest, SOCKET src,
  									 pid_t childPid);
  static void read_inheritable_socket(SOCKET *dest, InheritableSocket *src);
  #endif
  
  
  /* Save critical backend variables into the BackendParameters struct */
  #ifndef WIN32
  static bool
  save_backend_variables(BackendParameters *param, Port *port)
  #else
  static bool
  save_backend_variables(BackendParameters *param, Port *port,
  					   HANDLE childProcess, pid_t childPid)
  #endif
  {
  	memcpy(&param->port, port, sizeof(Port));
  	if (!write_inheritable_socket(&param->portsocket, port->sock, childPid))
  		return false;
  
  	strlcpy(param->DataDir, DataDir, MAXPGPATH);
  
  	memcpy(&param->ListenSocket, &ListenSocket, sizeof(ListenSocket));
  
  	param->MyCancelKey = MyCancelKey;
  	param->MyPMChildSlot = MyPMChildSlot;
  
  #ifdef WIN32
  	param->ShmemProtectiveRegion = ShmemProtectiveRegion;
  #endif
  	param->UsedShmemSegID = UsedShmemSegID;
  	param->UsedShmemSegAddr = UsedShmemSegAddr;
  
  	param->ShmemLock = ShmemLock;
  	param->ShmemVariableCache = ShmemVariableCache;
  	param->ShmemBackendArray = ShmemBackendArray;
  
  #ifndef HAVE_SPINLOCKS
  	param->SpinlockSemaArray = SpinlockSemaArray;
  #endif
  	param->NamedLWLockTrancheRequests = NamedLWLockTrancheRequests;
  	param->NamedLWLockTrancheArray = NamedLWLockTrancheArray;
  	param->MainLWLockArray = MainLWLockArray;
  	param->ProcStructLock = ProcStructLock;
  	param->ProcGlobal = ProcGlobal;
  	param->AuxiliaryProcs = AuxiliaryProcs;
  	param->PreparedXactProcs = PreparedXactProcs;
  	param->PMSignalState = PMSignalState;
  
  	param->PostmasterPid = PostmasterPid;
  	param->PgStartTime = PgStartTime;
  	param->PgReloadTime = PgReloadTime;
  	param->first_syslogger_file_time = first_syslogger_file_time;
  
  	param->redirection_done = redirection_done;
  	param->IsBinaryUpgrade = IsBinaryUpgrade;
  	param->query_id_enabled = query_id_enabled;
  	param->max_safe_fds = max_safe_fds;
  
  	param->MaxBackends = GetMaxBackends();
  
  #ifdef WIN32
  	param->PostmasterHandle = PostmasterHandle;
  	if (!write_duplicated_handle(&param->initial_signal_pipe,
  								 pgwin32_create_signal_listener(childPid),
  								 childProcess))
  		return false;
  #else
  	memcpy(&param->postmaster_alive_fds, &postmaster_alive_fds,
  		   sizeof(postmaster_alive_fds));
  #endif
  
  	memcpy(&param->syslogPipe, &syslogPipe, sizeof(syslogPipe));
  
  	strlcpy(param->my_exec_path, my_exec_path, MAXPGPATH);
  
  	strlcpy(param->pkglib_path, pkglib_path, MAXPGPATH);
  
  	return true;
  }
  
  
  #ifdef WIN32
  /*
   * Duplicate a handle for usage in a child process, and write the child
   * process instance of the handle to the parameter file.
   */
  static bool
  write_duplicated_handle(HANDLE *dest, HANDLE src, HANDLE childProcess)
  {
  	HANDLE		hChild = INVALID_HANDLE_VALUE;
  
  	if (!DuplicateHandle(GetCurrentProcess(),
  						 src,
  						 childProcess,
  						 &hChild,
  						 0,
  						 TRUE,
  						 DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS))
  	{
  		ereport(LOG,
  				(errmsg_internal("could not duplicate handle to be written to backend parameter file: error code %lu",
  								 GetLastError())));
  		return false;
  	}
  
  	*dest = hChild;
  	return true;
  }
  
  /*
   * Duplicate a socket for usage in a child process, and write the resulting
   * structure to the parameter file.
   * This is required because a number of LSPs (Layered Service Providers) very
   * common on Windows (antivirus, firewalls, download managers etc) break
   * straight socket inheritance.
   */
  static bool
  write_inheritable_socket(InheritableSocket *dest, SOCKET src, pid_t childpid)
  {
  	dest->origsocket = src;
  	if (src != 0 && src != PGINVALID_SOCKET)
  	{
  		/* Actual socket */
  		if (WSADuplicateSocket(src, childpid, &dest->wsainfo) != 0)
  		{
  			ereport(LOG,
  					(errmsg("could not duplicate socket %d for use in backend: error code %d",
  							(int) src, WSAGetLastError())));
  			return false;
  		}
  	}
  	return true;
  }
  
  /*
   * Read a duplicate socket structure back, and get the socket descriptor.
   */
  static void
  read_inheritable_socket(SOCKET *dest, InheritableSocket *src)
  {
  	SOCKET		s;
  
  	if (src->origsocket == PGINVALID_SOCKET || src->origsocket == 0)
  	{
  		/* Not a real socket! */
  		*dest = src->origsocket;
  	}
  	else
  	{
  		/* Actual socket, so create from structure */
  		s = WSASocket(FROM_PROTOCOL_INFO,
  					  FROM_PROTOCOL_INFO,
  					  FROM_PROTOCOL_INFO,
  					  &src->wsainfo,
  					  0,
  					  0);
  		if (s == INVALID_SOCKET)
  		{
  			write_stderr("could not create inherited socket: error code %d\n",
  						 WSAGetLastError());
  			exit(1);
  		}
  		*dest = s;
  
  		/*
  		 * To make sure we don't get two references to the same socket, close
  		 * the original one. (This would happen when inheritance actually
  		 * works..
  		 */
  		closesocket(src->origsocket);
  	}
  }
  #endif
  
  static void
  read_backend_variables(char *id, Port *port)
  {
  	BackendParameters param;
  
  #ifndef WIN32
  	/* Non-win32 implementation reads from file */
  	FILE	   *fp;
  
  	/* Open file */
  	fp = AllocateFile(id, PG_BINARY_R);
  	if (!fp)
  	{
  		write_stderr("could not open backend variables file \"%s\": %s\n",
  					 id, strerror(errno));
  		exit(1);
  	}
  
  	if (fread(&param, sizeof(param), 1, fp) != 1)
  	{
  		write_stderr("could not read from backend variables file \"%s\": %s\n",
  					 id, strerror(errno));
  		exit(1);
  	}
  
  	/* Release file */
  	FreeFile(fp);
  	if (unlink(id) != 0)
  	{
  		write_stderr("could not remove file \"%s\": %s\n",
  					 id, strerror(errno));
  		exit(1);
  	}
  #else
  	/* Win32 version uses mapped file */
  	HANDLE		paramHandle;
  	BackendParameters *paramp;
  
  #ifdef _WIN64
  	paramHandle = (HANDLE) _atoi64(id);
  #else
  	paramHandle = (HANDLE) atol(id);
  #endif
  	paramp = MapViewOfFile(paramHandle, FILE_MAP_READ, 0, 0, 0);
  	if (!paramp)
  	{
  		write_stderr("could not map view of backend variables: error code %lu\n",
  					 GetLastError());
  		exit(1);
  	}
  
  	memcpy(&param, paramp, sizeof(BackendParameters));
  
  	if (!UnmapViewOfFile(paramp))
  	{
  		write_stderr("could not unmap view of backend variables: error code %lu\n",
  					 GetLastError());
  		exit(1);
  	}
  
  	if (!CloseHandle(paramHandle))
  	{
  		write_stderr("could not close handle to backend parameter variables: error code %lu\n",
  					 GetLastError());
  		exit(1);
  	}
  #endif
  
  	restore_backend_variables(&param, port);
  }
  
  /* Restore critical backend variables from the BackendParameters struct */
  static void
  restore_backend_variables(BackendParameters *param, Port *port)
  {
  	memcpy(port, &param->port, sizeof(Port));
  	read_inheritable_socket(&port->sock, &param->portsocket);
  
  	SetDataDir(param->DataDir);
  
  	memcpy(&ListenSocket, &param->ListenSocket, sizeof(ListenSocket));
  
  	MyCancelKey = param->MyCancelKey;
  	MyPMChildSlot = param->MyPMChildSlot;
  
  #ifdef WIN32
  	ShmemProtectiveRegion = param->ShmemProtectiveRegion;
  #endif
  	UsedShmemSegID = param->UsedShmemSegID;
  	UsedShmemSegAddr = param->UsedShmemSegAddr;
  
  	ShmemLock = param->ShmemLock;
  	ShmemVariableCache = param->ShmemVariableCache;
  	ShmemBackendArray = param->ShmemBackendArray;
  
  #ifndef HAVE_SPINLOCKS
  	SpinlockSemaArray = param->SpinlockSemaArray;
  #endif
  	NamedLWLockTrancheRequests = param->NamedLWLockTrancheRequests;
  	NamedLWLockTrancheArray = param->NamedLWLockTrancheArray;
  	MainLWLockArray = param->MainLWLockArray;
  	ProcStructLock = param->ProcStructLock;
  	ProcGlobal = param->ProcGlobal;
  	AuxiliaryProcs = param->AuxiliaryProcs;
  	PreparedXactProcs = param->PreparedXactProcs;
  	PMSignalState = param->PMSignalState;
  
  	PostmasterPid = param->PostmasterPid;
  	PgStartTime = param->PgStartTime;
  	PgReloadTime = param->PgReloadTime;
  	first_syslogger_file_time = param->first_syslogger_file_time;
  
  	redirection_done = param->redirection_done;
  	IsBinaryUpgrade = param->IsBinaryUpgrade;
  	query_id_enabled = param->query_id_enabled;
  	max_safe_fds = param->max_safe_fds;
  
  	SetMaxBackends(param->MaxBackends);
  
  #ifdef WIN32
  	PostmasterHandle = param->PostmasterHandle;
  	pgwin32_initial_signal_pipe = param->initial_signal_pipe;
  #else
  	memcpy(&postmaster_alive_fds, &param->postmaster_alive_fds,
  		   sizeof(postmaster_alive_fds));
  #endif
  
  	memcpy(&syslogPipe, &param->syslogPipe, sizeof(syslogPipe));
  
  	strlcpy(my_exec_path, param->my_exec_path, MAXPGPATH);
  
  	strlcpy(pkglib_path, param->pkglib_path, MAXPGPATH);
  
  	/*
  	 * We need to restore fd.c's counts of externally-opened FDs; to avoid
  	 * confusion, be sure to do this after restoring max_safe_fds.  (Note:
  	 * BackendInitialize will handle this for port->sock.)
  	 */
  #ifndef WIN32
  	if (postmaster_alive_fds[0] >= 0)
  		ReserveExternalFD();
  	if (postmaster_alive_fds[1] >= 0)
  		ReserveExternalFD();
  #endif
  }
  
  
  Size
  ShmemBackendArraySize(void)
  {
  	return mul_size(MaxLivePostmasterChildren(), sizeof(Backend));
  }
  
  void
  ShmemBackendArrayAllocation(void)
  {
  	Size		size = ShmemBackendArraySize();
  
  	ShmemBackendArray = (Backend *) ShmemAlloc(size);
  	/* Mark all slots as empty */
  	memset(ShmemBackendArray, 0, size);
  }
  
  static void
  ShmemBackendArrayAdd(Backend *bn)
  {
  	/* The array slot corresponding to my PMChildSlot should be free */
  	int			i = bn->child_slot - 1;
  
  	Assert(ShmemBackendArray[i].pid == 0);
  	ShmemBackendArray[i] = *bn;
  }
  
  static void
  ShmemBackendArrayRemove(Backend *bn)
  {
  	int			i = bn->child_slot - 1;
  
  	Assert(ShmemBackendArray[i].pid == bn->pid);
  	/* Mark the slot as empty */
  	ShmemBackendArray[i].pid = 0;
  }
  #endif							/* EXEC_BACKEND */
  
  
  #ifdef WIN32
  
  /*
   * Subset implementation of waitpid() for Windows.  We assume pid is -1
   * (that is, check all child processes) and options is WNOHANG (don't wait).
   */
  static pid_t
  waitpid(pid_t pid, int *exitstatus, int options)
  {
  	DWORD		dwd;
  	ULONG_PTR	key;
  	OVERLAPPED *ovl;
  
  	/*
  	 * Check if there are any dead children. If there are, return the pid of
  	 * the first one that died.
  	 */
  	if (GetQueuedCompletionStatus(win32ChildQueue, &dwd, &key, &ovl, 0))
  	{
  		*exitstatus = (int) key;
  		return dwd;
  	}
  
  	return -1;
  }
  
  /*
   * Note! Code below executes on a thread pool! All operations must
   * be thread safe! Note that elog() and friends must *not* be used.
   */
  static void WINAPI
  pgwin32_deadchild_callback(PVOID lpParameter, BOOLEAN TimerOrWaitFired)
  {
  	win32_deadchild_waitinfo *childinfo = (win32_deadchild_waitinfo *) lpParameter;
  	DWORD		exitcode;
  
  	if (TimerOrWaitFired)
  		return;					/* timeout. Should never happen, since we use
  								 * INFINITE as timeout value. */
  
  	/*
  	 * Remove handle from wait - required even though it's set to wait only
  	 * once
  	 */
  	UnregisterWaitEx(childinfo->waitHandle, NULL);
  
  	if (!GetExitCodeProcess(childinfo->procHandle, &exitcode))
  	{
  		/*
  		 * Should never happen. Inform user and set a fixed exitcode.
  		 */
  		write_stderr("could not read exit code for process\n");
  		exitcode = 255;
  	}
  
  	if (!PostQueuedCompletionStatus(win32ChildQueue, childinfo->procId, (ULONG_PTR) exitcode, NULL))
  		write_stderr("could not post child completion status\n");
  
  	/*
  	 * Handle is per-process, so we close it here instead of in the
  	 * originating thread
  	 */
  	CloseHandle(childinfo->procHandle);
  
  	/*
  	 * Free struct that was allocated before the call to
  	 * RegisterWaitForSingleObject()
  	 */
  	free(childinfo);
  
  	/* Queue SIGCHLD signal */
  	pg_queue_signal(SIGCHLD);
  }
  #endif							/* WIN32 */
  
  /*
   * Initialize one and only handle for monitoring postmaster death.
   *
   * Called once in the postmaster, so that child processes can subsequently
   * monitor if their parent is dead.
   */
  static void
  InitPostmasterDeathWatchHandle(void)
  {
  #ifndef WIN32
  
  	/*
  	 * Create a pipe. Postmaster holds the write end of the pipe open
  	 * (POSTMASTER_FD_OWN), and children hold the read end. Children can pass
  	 * the read file descriptor to select() to wake up in case postmaster
  	 * dies, or check for postmaster death with a (read() == 0). Children must
  	 * close the write end as soon as possible after forking, because EOF
  	 * won't be signaled in the read end until all processes have closed the
  	 * write fd. That is taken care of in ClosePostmasterPorts().
  	 */
  	Assert(MyProcPid == PostmasterPid);
  	if (pipe(postmaster_alive_fds) < 0)
  		ereport(FATAL,
  				(errcode_for_file_access(),
  				 errmsg_internal("could not create pipe to monitor postmaster death: %m")));
  
  	/* Notify fd.c that we've eaten two FDs for the pipe. */
  	ReserveExternalFD();
  	ReserveExternalFD();
  
  	/*
  	 * Set O_NONBLOCK to allow testing for the fd's presence with a read()
  	 * call.
  	 */
  	if (fcntl(postmaster_alive_fds[POSTMASTER_FD_WATCH], F_SETFL, O_NONBLOCK) == -1)
  		ereport(FATAL,
  				(errcode_for_socket_access(),
  				 errmsg_internal("could not set postmaster death monitoring pipe to nonblocking mode: %m")));
  #else
  
  	/*
  	 * On Windows, we use a process handle for the same purpose.
  	 */
  	if (DuplicateHandle(GetCurrentProcess(),
  						GetCurrentProcess(),
  						GetCurrentProcess(),
  						&PostmasterHandle,
  						0,
  						TRUE,
  						DUPLICATE_SAME_ACCESS) == 0)
  		ereport(FATAL,
  				(errmsg_internal("could not duplicate postmaster handle: error code %lu",
  								 GetLastError())));
  #endif							/* WIN32 */
  }
  