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) 1996-2014, 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 <netinet/in.h>
  #include <arpa/inet.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
  
  #include "access/transam.h"
  #include "access/xlog.h"
  #include "bootstrap/bootstrap.h"
  #include "catalog/pg_control.h"
  #include "lib/ilist.h"
  #include "libpq/auth.h"
  #include "libpq/ip.h"
  #include "libpq/libpq.h"
  #include "libpq/pqsignal.h"
  #include "miscadmin.h"
  #include "pg_getopt.h"
  #include "pgstat.h"
  #include "postmaster/autovacuum.h"
  #include "postmaster/bgworker_internals.h"
  #include "postmaster/fork_process.h"
  #include "postmaster/pgarch.h"
  #include "postmaster/postmaster.h"
  #include "postmaster/syslogger.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/dynamic_loader.h"
  #include "utils/memutils.h"
  #include "utils/ps_status.h"
  #include "utils/timeout.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 */
  
  #define BACKEND_TYPE_WORKER		(BACKEND_TYPE_AUTOVAC | BACKEND_TYPE_BGWORKER)
  
  /*
   * 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.
   *
   * "Special" children such as the startup, bgwriter and autovacuum launcher
   * tasks are not in this list.	Autovacuum worker and walsender are in it.
   * 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.
   *
   * Background workers that request shared memory access during registration are
   * in this list, too.
   */
  typedef struct bkend
  {
  	pid_t		pid;			/* process id of backend */
  	long		cancel_key;		/* cancel key for cancels for this backend */
  	int			child_slot;		/* PMChildSlot for this backend, if any */
  
  	/*
  	 * Flavor of backend or auxiliary process.	Note that BACKEND_TYPE_WALSND
  	 * backends initially announce themselves as BACKEND_TYPE_NORMAL, so if
  	 * bkend_type is normal, you should check for a recent transition.
  	 */
  	int			bkend_type;
  	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 MaxBackends so
   * number of backend slots available to non-superusers is
   * (MaxBackends - 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];
  
  /*
   * Set by the -o option
   */
  static char ExtraOptions[MAXPGPATH];
  
  /*
   * 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;
  
  /* 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,
  			PgStatPID = 0,
  			SysLoggerPID = 0;
  
  /* 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 */
  static bool RecoveryError = false;		/* T if WAL recovery failed */
  
  /*
   * 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.  (We also allow launch of normal
   * child backends in PM_WAIT_BACKUP state, but only for superusers.)
   * 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_* 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.
   * Similarly, RecoveryError means that we have crashed during recovery, and
   * should not try to restart.
   */
  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_WAIT_BACKUP,				/* waiting for online backup mode to end */
  	PM_WAIT_READONLY,			/* waiting for read only backends to exit */
  	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;
  
  /* Start time of abort processing at immediate shutdown or child crash */
  static time_t AbortStartTime;
  #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 signalled to communicate some condition */
  static volatile bool avlauncher_needs_signal = false;
  
  /* set when there's a worker that needs to be started up */
  static volatile bool StartWorkerNeeded = true;
  static volatile bool HaveCrashedWorker = false;
  
  /*
   * State for assigning random salts and cancel keys.
   * Also, the global MyCancelKey passes the cancel key assigned to a given
   * backend from the postmaster to that backend (via fork).
   */
  static unsigned int random_seed = 0;
  static struct timeval random_start_time;
  
  #ifdef USE_BONJOUR
  static DNSServiceRef bonjour_sdref = NULL;
  #endif
  
  /*
   * postmaster.c - function prototypes
   */
  static void unlink_external_pid_file(int status, Datum arg);
  static void getInstallationPaths(const char *argv0);
  static void checkDataDir(void);
  static Port *ConnCreate(int serverFd);
  static void ConnFree(Port *port);
  static void reset_shared(int port);
  static void SIGHUP_handler(SIGNAL_ARGS);
  static void pmdie(SIGNAL_ARGS);
  static void reaper(SIGNAL_ARGS);
  static void sigusr1_handler(SIGNAL_ARGS);
  static void startup_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) __attribute__((noreturn));
  static void ExitPostmaster(int status) __attribute__((noreturn));
  static int	ServerLoop(void);
  static int	BackendStartup(Port *port);
  static int	ProcessStartupPacket(Port *port, bool SSLdone);
  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(void);
  static long PostmasterRandom(void);
  static void RandomSalt(char *md5Salt);
  static void signal_child(pid_t pid, int signal);
  static bool SignalSomeChildren(int signal, int targets);
  static bool SignalUnconnectedWorkers(int signal);
  static void TerminateChildren(int signal);
  
  #define SignalChildren(sig)			   SignalSomeChildren(sig, BACKEND_TYPE_ALL)
  
  static int	CountChildren(int target);
  static int	CountUnconnectedWorkers(void);
  static void maybe_start_bgworker(void);
  static bool CreateOptsFile(int argc, char *argv[], char *fullprogname);
  static pid_t StartChildProcess(AuxProcType type);
  static void StartAutovacuumWorker(void);
  static void InitPostmasterDeathWatchHandle(void);
  
  #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];
  	long		MyCancelKey;
  	int			MyPMChildSlot;
  #ifndef WIN32
  	unsigned long UsedShmemSegID;
  #else
  	HANDLE		UsedShmemSegID;
  #endif
  	void	   *UsedShmemSegAddr;
  	slock_t    *ShmemLock;
  	VariableCache ShmemVariableCache;
  	Backend    *ShmemBackendArray;
  #ifndef HAVE_SPINLOCKS
  	PGSemaphore	SpinlockSemaArray;
  #endif
  	LWLockPadded *MainLWLockArray;
  	slock_t    *ProcStructLock;
  	PROC_HDR   *ProcGlobal;
  	PGPROC	   *AuxiliaryProcs;
  	PGPROC	   *PreparedXactProcs;
  	PMSignalData *PMSignalState;
  	InheritableSocket pgStatSock;
  	pid_t		PostmasterPid;
  	TimestampTz PgStartTime;
  	TimestampTz PgReloadTime;
  	pg_time_t	first_syslogger_file_time;
  	bool		redirection_done;
  	bool		IsBinaryUpgrade;
  	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];
  	char		ExtraOptions[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 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)
  
  #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;
  
  	MyProcPid = PostmasterPid = getpid();
  
  	MyStartTime = time(NULL);
  
  	IsPostmasterEnvironment = true;
  
  	/*
  	 * for security, no dir or file created can be group or other accessible
  	 */
  	umask(S_IRWXG | S_IRWXO);
  
  	/*
  	 * 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_MINSIZE,
  											  ALLOCSET_DEFAULT_INITSIZE,
  											  ALLOCSET_DEFAULT_MAXSIZE);
  	MemoryContextSwitchTo(PostmasterContext);
  
  	/* Initialize paths to installation files */
  	getInstallationPaths(argv[0]);
  
  	/*
  	 * 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, "A:B:bc:C:D:d:EeFf:h:ijk:lN:nOo:Pp:r:S:sTt:W:-:")) != -1)
  	{
  		switch (opt)
  		{
  			case 'A':
  				SetConfigOption("debug_assertions", optarg, PGC_POSTMASTER, PGC_S_ARGV);
  				break;
  
  			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 'o':
  				/* Other options to pass to the backend on the command line */
  				snprintf(ExtraOptions + strlen(ExtraOptions),
  						 sizeof(ExtraOptions) - strlen(ExtraOptions),
  						 " %s", optarg);
  				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)
  	{
  		/*
  		 * permission is handled because the user is reading inside the data
  		 * dir
  		 */
  		puts(GetConfigOption(output_config_variable, false, false));
  		ExitPostmaster(0);
  	}
  
  	/* Verify that DataDir looks reasonable */
  	checkDataDir();
  
  	/* And switch working directory into it */
  	ChangeToDataDir();
  
  	/*
  	 * Check for invalid combinations of GUC settings.
  	 */
  	if (ReservedBackends >= MaxConnections)
  	{
  		write_stderr("%s: superuser_reserved_connections must be less than max_connections\n", progname);
  		ExitPostmaster(1);
  	}
  	if (max_wal_senders >= MaxConnections)
  	{
  		write_stderr("%s: max_wal_senders must be less than max_connections\n", progname);
  		ExitPostmaster(1);
  	}
  	if (XLogArchiveMode && wal_level == WAL_LEVEL_MINIMAL)
  		ereport(ERROR,
  				(errmsg("WAL archival (archive_mode=on) requires wal_level \"archive\", \"hot_standby\" or \"logical\"")));
  	if (max_wal_senders > 0 && wal_level == WAL_LEVEL_MINIMAL)
  		ereport(ERROR,
  				(errmsg("WAL streaming (max_wal_senders > 0) requires wal_level \"archive\", \"hot_standby\" 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).
  	 */
  	CreateDataDirLockFile(true);
  
  	/*
  	 * Initialize SSL library, if specified.
  	 */
  #ifdef USE_SSL
  	if (EnableSSL)
  		secure_initialize();
  #endif
  
  	/*
  	 * process any libraries that should be preloaded at postmaster start
  	 */
  	process_shared_preload_libraries();
  
  	/*
  	 * Now that loadable modules have had their chance to register background
  	 * workers, calculate MaxBackends.
  	 */
  	InitializeMaxBackends();
  
  	/*
  	 * Establish input sockets.
  	 */
  	for (i = 0; i < MAXLISTEN; i++)
  		ListenSocket[i] = PGINVALID_SOCKET;
  
  	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 (!SplitIdentifierString(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,
  								 htons(PostPortNumber),
  								 0,
  								 NULL,
  								 NULL,
  								 NULL);
  		if (err != kDNSServiceErr_NoError)
  			elog(LOG, "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, "");
  
  	/*
  	 * Set up shared memory and semaphores.
  	 */
  	reset_shared(PostPortNumber);
  
  	/*
  	 * 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.
  	 */
  	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
  
  	/*
  	 * Record postmaster options.  We delay this till now to avoid recording
  	 * bogus options (eg, NBuffers too high for available memory).
  	 */
  	if (!CreateOptsFile(argc, argv, my_exec_path))
  		ExitPostmaster(1);
  
  #ifdef EXEC_BACKEND
  	/* Write out nondefault GUC settings for child processes to use */
  	write_nondefault_variables(PGC_POSTMASTER);
  #endif
  
  	/*
  	 * 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);
  	}
  
  	/*
  	 * Set up signal handlers for the postmaster process.
  	 *
  	 * 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/pgstat.c,
  	 * postmaster/syslogger.c, postmaster/bgworker.c and
  	 * postmaster/checkpointer.c.
  	 */
  	pqinitmask();
  	PG_SETMASK(&BlockSig);
  
  	pqsignal(SIGHUP, SIGHUP_handler);	/* reread config file and have
  										 * children do same */
  	pqsignal(SIGINT, pmdie);	/* send SIGTERM and shut down */
  	pqsignal(SIGQUIT, pmdie);	/* send SIGQUIT and die */
  	pqsignal(SIGTERM, pmdie);	/* wait for children and shut down */
  	pqsignal(SIGALRM, SIG_IGN); /* ignored */
  	pqsignal(SIGPIPE, SIG_IGN); /* ignored */
  	pqsignal(SIGUSR1, sigusr1_handler); /* message from child process */
  	pqsignal(SIGUSR2, dummy_handler);	/* unused, reserve for children */
  	pqsignal(SIGCHLD, reaper);	/* handle child termination */
  	pqsignal(SIGTTIN, SIG_IGN); /* ignored */
  	pqsignal(SIGTTOU, SIG_IGN); /* ignored */
  	/* ignore SIGXFSZ, so that ulimit violations work like disk full */
  #ifdef SIGXFSZ
  	pqsignal(SIGXFSZ, SIG_IGN); /* ignored */
  #endif
  
  	/*
  	 * 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;
  
  	/*
  	 * Initialize stats collection subsystem (this does NOT start the
  	 * collector process!)
  	 */
  	pgstat_init();
  
  	/*
  	 * 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.
  		 */
  	}
  
  
  	/*
  	 * Remove old temporary files.	At this point there can be no other
  	 * Postgres processes running in this directory, so this should be safe.
  	 */
  	RemovePgTempFiles();
  
  	/*
  	 * Remember postmaster startup time
  	 */
  	PgStartTime = GetCurrentTimestamp();
  	/* PostmasterRandom wants its own copy */
  	gettimeofday(&random_start_time, NULL);
  
  	/*
  	 * We're ready to rock and roll...
  	 */
  	StartupPID = StartupDataBase();
  	Assert(StartupPID != 0);
  	pmState = PM_STARTUP;
  
  	/* Some workers may be scheduled to start now */
  	maybe_start_bgworker();
  
  	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 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)
  		elog(FATAL, "%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.
  	 */
  }
  
  
  /*
   * Validate the proposed data directory
   */
  static void
  checkDataDir(void)
  {
  	char		path[MAXPGPATH];
  	FILE	   *fp;
  	struct stat stat_buf;
  
  	Assert(DataDir);
  
  	if (stat(DataDir, &stat_buf) != 0)
  	{
  		if (errno == ENOENT)
  			ereport(FATAL,
  					(errcode_for_file_access(),
  					 errmsg("data directory \"%s\" does not exist",
  							DataDir)));
  		else
  			ereport(FATAL,
  					(errcode_for_file_access(),
  				 errmsg("could not read permissions of directory \"%s\": %m",
  						DataDir)));
  	}
  
  	/* eventual chdir would fail anyway, but let's test ... */
  	if (!S_ISDIR(stat_buf.st_mode))
  		ereport(FATAL,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("specified data directory \"%s\" is not a directory",
  						DataDir)));
  
  	/*
  	 * Check that the directory belongs to my userid; if not, reject.
  	 *
  	 * This check is an essential part of the interlock that prevents two
  	 * postmasters from starting in the same directory (see CreateLockFile()).
  	 * Do not remove or weaken it.
  	 *
  	 * XXX can we safely enable this check on Windows?
  	 */
  #if !defined(WIN32) && !defined(__CYGWIN__)
  	if (stat_buf.st_uid != geteuid())
  		ereport(FATAL,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("data directory \"%s\" has wrong ownership",
  						DataDir),
  				 errhint("The server must be started by the user that owns the data directory.")));
  #endif
  
  	/*
  	 * Check if the directory has group or world access.  If so, reject.
  	 *
  	 * It would be possible to allow weaker constraints (for example, allow
  	 * group access) but we cannot make a general assumption that that is
  	 * okay; for example there are platforms where nearly all users
  	 * customarily belong to the same group.  Perhaps this test should be
  	 * configurable.
  	 *
  	 * XXX temporarily suppress check when on Windows, because there may not
  	 * be proper support for Unix-y file permissions.  Need to think of a
  	 * reasonable check to apply on Windows.
  	 */
  #if !defined(WIN32) && !defined(__CYGWIN__)
  	if (stat_buf.st_mode & (S_IRWXG | S_IRWXO))
  		ereport(FATAL,
  				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
  				 errmsg("data directory \"%s\" has group or world access",
  						DataDir),
  				 errdetail("Permissions should be u=rwx (0700).")));
  #endif
  
  	/* Look for PG_VERSION before looking for pg_control */
  	ValidatePgVersion(DataDir);
  
  	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.
   */
  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 = Max(SIGKILL_CHILDREN_AFTER_SECS -
  								  (time(NULL) - AbortStartTime), 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
   */
  static int
  ServerLoop(void)
  {
  	fd_set		readmask;
  	int			nSockets;
  	time_t		now,
  				last_touch_time;
  
  	last_touch_time = time(NULL);
  
  	nSockets = initMasks(&readmask);
  
  	for (;;)
  	{
  		fd_set		rmask;
  		int			selres;
  
  		/*
  		 * Wait for a connection request to arrive.
  		 *
  		 * 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() at all; just sleep
  		 * for a little bit with signals unblocked.
  		 */
  		memcpy((char *) &rmask, (char *) &readmask, sizeof(fd_set));
  
  		PG_SETMASK(&UnBlockSig);
  
  		if (pmState == PM_WAIT_DEAD_END)
  		{
  			pg_usleep(100000L); /* 100 msec seems reasonable */
  			selres = 0;
  		}
  		else
  		{
  			/* must set timeout each time; some OSes change it! */
  			struct timeval timeout;
  
  			DetermineSleepTime(&timeout);
  
  			selres = select(nSockets, &rmask, NULL, NULL, &timeout);
  		}
  
  		/*
  		 * Block all signals until we wait again.  (This makes it safe for our
  		 * signal handlers to do nontrivial work.)
  		 */
  		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)
  		{
  			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 (XLogArchivingActive() && PgArchPID == 0 && pmState == PM_RUN)
  			PgArchPID = pgarch_start();
  
  		/* If we have lost the stats collector, try to start a new one */
  		if (PgStatPID == 0 && pmState == PM_RUN)
  			PgStatPID = pgstat_start();
  
  		/* 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);
  		}
  
  		/* Get other worker processes running, if needed */
  		if (StartWorkerNeeded || HaveCrashedWorker)
  			maybe_start_bgworker();
  
  		/*
  		 * 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 ...
  		 */
  		now = time(NULL);
  		if (now - last_touch_time >= 58 * SECS_PER_MINUTE)
  		{
  			TouchSocketFiles();
  			TouchSocketLockFiles();
  			last_touch_time = now;
  		}
  
  		/*
  		 * 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 */
  			TerminateChildren(SIGKILL);
  			/* reset flag so we don't SIGKILL again */
  			AbortStartTime = 0;
  
  			/*
  			 * Additionally, unless we're recovering from a process crash, it's
  			 * now the time for postmaster to abandon ship.
  			 */
  			if (!FatalError)
  				ExitPostmaster(1);
  		}
  	}
  }
  
  /*
   * 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.)
   */
  static int
  ProcessStartupPacket(Port *port, bool SSLdone)
  {
  	int32		len;
  	void	   *buf;
  	ProtocolVersion proto;
  	MemoryContext oldcontext;
  
  	if (pq_getbytes((char *) &len, 4) == EOF)
  	{
  		/*
  		 * EOF after SSLdone probably means the client didn't like our
  		 * response to NEGOTIATE_SSL_CODE.	That's not an error condition, so
  		 * don't clutter the log with a complaint.
  		 */
  		if (!SSLdone)
  			ereport(COMMERROR,
  					(errcode(ERRCODE_PROTOCOL_VIOLATION),
  					 errmsg("incomplete startup packet")));
  		return STATUS_ERROR;
  	}
  
  	len = ntohl(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 at least the size of an old-style startup packet, plus one
  	 * extra byte, and make sure all are zeroes.  This ensures we will have
  	 * null termination of all strings, in both fixed- and variable-length
  	 * packet layouts.
  	 */
  	if (len <= (int32) sizeof(StartupPacket))
  		buf = palloc0(sizeof(StartupPacket) + 1);
  	else
  		buf = palloc0(len + 1);
  
  	if (pq_getbytes(buf, len) == EOF)
  	{
  		ereport(COMMERROR,
  				(errcode(ERRCODE_PROTOCOL_VIOLATION),
  				 errmsg("incomplete startup packet")));
  		return STATUS_ERROR;
  	}
  
  	/*
  	 * The first field is either a protocol version number or a special
  	 * request code.
  	 */
  	port->proto = proto = ntohl(*((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 && !SSLdone)
  	{
  		char		SSLok;
  
  #ifdef USE_SSL
  		/* No SSL when disabled or on Unix sockets */
  		if (!EnableSSL || IS_AF_UNIX(port->laddr.addr.ss_family))
  			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
  		/* regular startup packet, cancel, etc packet should follow... */
  		/* but not another SSL negotiation request */
  		return ProcessStartupPacket(port, 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 we can handle the protocol the frontend is using. */
  
  	if (PG_PROTOCOL_MAJOR(proto) < PG_PROTOCOL_MAJOR(PG_PROTOCOL_EARLIEST) ||
  		PG_PROTOCOL_MAJOR(proto) > PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST) ||
  		(PG_PROTOCOL_MAJOR(proto) == PG_PROTOCOL_MAJOR(PG_PROTOCOL_LATEST) &&
  		 PG_PROTOCOL_MINOR(proto) > PG_PROTOCOL_MINOR(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);
  
  	if (PG_PROTOCOL_MAJOR(proto) >= 3)
  	{
  		int32		offset = sizeof(ProtocolVersion);
  
  		/*
  		 * 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 = ((char *) 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 = ((char *) 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)
  			{
  				if (!parse_bool(valptr, &am_walsender))
  					ereport(FATAL,
  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
  							 errmsg("invalid value for boolean option \"replication\"")));
  			}
  			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));
  			}
  			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")));
  	}
  	else
  	{
  		/*
  		 * Get the parameters from the old-style, fixed-width-fields startup
  		 * packet as C strings.  The packet destination was cleared first so a
  		 * short packet has zeros silently added.  We have to be prepared to
  		 * truncate the pstrdup result for oversize fields, though.
  		 */
  		StartupPacket *packet = (StartupPacket *) buf;
  
  		port->database_name = pstrdup(packet->database);
  		if (strlen(port->database_name) > sizeof(packet->database))
  			port->database_name[sizeof(packet->database)] = '\0';
  		port->user_name = pstrdup(packet->user);
  		if (strlen(port->user_name) > sizeof(packet->user))
  			port->user_name[sizeof(packet->user)] = '\0';
  		port->cmdline_options = pstrdup(packet->options);
  		if (strlen(port->cmdline_options) > sizeof(packet->options))
  			port->cmdline_options[sizeof(packet->options)] = '\0';
  		port->guc_options = NIL;
  	}
  
  	/* 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';
  
  	/* Walsender is not related to a particular database */
  	if (am_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_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_WAITBACKUP:
  			/* OK for now, will check in InitPostgres */
  			break;
  		case CAC_OK:
  			break;
  	}
  
  	return STATUS_OK;
  }
  
  
  /*
   * 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;
  	long		cancelAuthCode;
  	Backend    *bp;
  
  #ifndef EXEC_BACKEND
  	dlist_iter	iter;
  #else
  	int			i;
  #endif
  
  	backendPID = (int) ntohl(canc->backendPID);
  	cancelAuthCode = (long) ntohl(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;
  		}
  	}
  
  	/* 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.
   */
  static CAC_state
  canAcceptConnections(void)
  {
  	CAC_state	result = CAC_OK;
  
  	/*
  	 * Can't start backends when in startup/shutdown/inconsistent recovery
  	 * state.
  	 *
  	 * In state PM_WAIT_BACKUP only superusers can connect (this must be
  	 * allowed so that a superuser can end online backup mode); we return
  	 * CAC_WAITBACKUP code to indicate that this must be checked later. Note
  	 * that neither CAC_OK nor CAC_WAITBACKUP can safely be returned until we
  	 * have checked for too many children.
  	 */
  	if (pmState != PM_RUN)
  	{
  		if (pmState == PM_WAIT_BACKUP)
  			result = CAC_WAITBACKUP;	/* allow superusers only */
  		else if (Shutdown > NoShutdown)
  			return CAC_SHUTDOWN;	/* shutdown is pending */
  		else if (!FatalError &&
  				 (pmState == PM_STARTUP ||
  				  pmState == PM_RECOVERY))
  			return CAC_STARTUP; /* normal startup */
  		else if (!FatalError &&
  				 pmState == PM_HOT_STANDBY)
  			result = CAC_OK;	/* connection OK during hot standby */
  		else
  			return CAC_RECOVERY;	/* else must be crash recovery */
  	}
  
  	/*
  	 * Don't start too many children.
  	 *
  	 * We allow more connections than we can have backends here 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 >= 0)
  			StreamClose(port->sock);
  		ConnFree(port);
  		return NULL;
  	}
  
  	/*
  	 * Precompute password salt values to use for this connection. It's
  	 * slightly annoying to do this long in advance of knowing whether we'll
  	 * need 'em or not, but we must do the random() calls before we fork, not
  	 * after.  Else the postmaster's random sequence won't get advanced, and
  	 * all backends would end up using the same salt...
  	 */
  	RandomSalt(port->md5Salt);
  
  	/*
  	 * Allocate GSSAPI specific state struct
  	 */
  #ifndef EXEC_BACKEND
  #if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
  	port->gss = (pg_gssinfo *) calloc(1, sizeof(pg_gssinfo));
  	if (!port->gss)
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  		ExitPostmaster(1);
  	}
  #endif
  #endif
  
  	return port;
  }
  
  
  /*
   * ConnFree -- free a local connection data structure
   */
  static void
  ConnFree(Port *conn)
  {
  #ifdef USE_SSL
  	secure_close(conn);
  #endif
  	if (conn->gss)
  		free(conn->gss);
  	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]))
  		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;
  #endif
  
  	/* Close the listen sockets */
  	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 */
  	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
  }
  
  
  /*
   * reset_shared -- reset shared memory and semaphores
   */
  static void
  reset_shared(int port)
  {
  	/*
  	 * 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), since the port number is used to
  	 * determine IPC keys.	This helps ensure that we will clean up dead IPC
  	 * objects if the postmaster crashes and is restarted.
  	 */
  	CreateSharedMemoryAndSemaphores(false, port);
  }
  
  
  /*
   * SIGHUP -- reread config files, and tell children to do same
   */
  static void
  SIGHUP_handler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	PG_SETMASK(&BlockSig);
  
  	if (Shutdown <= SmartShutdown)
  	{
  		ereport(LOG,
  				(errmsg("received SIGHUP, reloading configuration files")));
  		ProcessConfigFile(PGC_SIGHUP);
  		SignalChildren(SIGHUP);
  		SignalUnconnectedWorkers(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);
  		if (PgStatPID != 0)
  			signal_child(PgStatPID, SIGHUP);
  
  		/* Reload authentication config files too */
  		if (!load_hba())
  			ereport(WARNING,
  					(errmsg("pg_hba.conf not reloaded")));
  
  		if (!load_ident())
  			ereport(WARNING,
  					(errmsg("pg_ident.conf not reloaded")));
  
  #ifdef EXEC_BACKEND
  		/* Update the starting-point file for future children */
  		write_nondefault_variables(PGC_SIGHUP);
  #endif
  	}
  
  	PG_SETMASK(&UnBlockSig);
  
  	errno = save_errno;
  }
  
  
  /*
   * pmdie -- signal handler for processing various postmaster signals.
   */
  static void
  pmdie(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	PG_SETMASK(&BlockSig);
  
  	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")));
  
  			if (pmState == PM_RUN || pmState == PM_RECOVERY ||
  				pmState == PM_HOT_STANDBY || pmState == PM_STARTUP)
  			{
  				/* autovac workers are told to shut down immediately */
  				/* and bgworkers too; does this need tweaking? */
  				SignalSomeChildren(SIGTERM,
  							   BACKEND_TYPE_AUTOVAC | BACKEND_TYPE_BGWORKER);
  				SignalUnconnectedWorkers(SIGTERM);
  				/* 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, we can't kill the startup process
  				 * right away, because at present doing so does not release
  				 * its locks.  We might want to change this in a future
  				 * release.  For the time being, the PM_WAIT_READONLY state
  				 * indicates that we're waiting for the regular (read only)
  				 * backends to die off; once they do, we'll kill the startup
  				 * and walreceiver processes.
  				 */
  				pmState = (pmState == PM_RUN) ?
  					PM_WAIT_BACKUP : PM_WAIT_READONLY;
  			}
  
  			/*
  			 * 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")));
  
  			if (StartupPID != 0)
  				signal_child(StartupPID, SIGTERM);
  			if (BgWriterPID != 0)
  				signal_child(BgWriterPID, SIGTERM);
  			if (WalReceiverPID != 0)
  				signal_child(WalReceiverPID, SIGTERM);
  			SignalUnconnectedWorkers(SIGTERM);
  			if (pmState == PM_RECOVERY)
  			{
  				/*
  				 * Only startup, bgwriter, walreceiver, unconnected bgworkers,
  				 * and/or checkpointer should be active in this state; we just
  				 * signaled the first four, and we don't want to kill
  				 * checkpointer yet.
  				 */
  				pmState = PM_WAIT_BACKENDS;
  			}
  			else if (pmState == PM_RUN ||
  					 pmState == PM_WAIT_BACKUP ||
  					 pmState == PM_WAIT_READONLY ||
  					 pmState == PM_WAIT_BACKENDS ||
  					 pmState == PM_HOT_STANDBY)
  			{
  				ereport(LOG,
  						(errmsg("aborting any active transactions")));
  				/* shut down all backends and workers */
  				SignalSomeChildren(SIGTERM,
  								 BACKEND_TYPE_NORMAL | BACKEND_TYPE_AUTOVAC |
  								   BACKEND_TYPE_BGWORKER);
  				/* and the autovac launcher too */
  				if (AutoVacPID != 0)
  					signal_child(AutoVacPID, SIGTERM);
  				/* and the walwriter too */
  				if (WalWriterPID != 0)
  					signal_child(WalWriterPID, SIGTERM);
  				pmState = PM_WAIT_BACKENDS;
  			}
  
  			/*
  			 * Now wait for backends to exit.  If there are none,
  			 * PostmasterStateMachine will take the next step.
  			 */
  			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")));
  
  			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;
  	}
  
  	PG_SETMASK(&UnBlockSig);
  
  	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 */
  
  	PG_SETMASK(&BlockSig);
  
  	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)))
  			{
  				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 && !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 RecoveryError so we don't try to reinitialize after
  			 * they're gone.  Exception: if FatalError is already set, that
  			 * implies 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.
  			 */
  			if (!EXIT_STATUS_0(exitstatus))
  			{
  				if (!FatalError)
  					RecoveryError = true;
  				HandleChildCrash(pid, exitstatus,
  								 _("startup process"));
  				continue;
  			}
  
  			/*
  			 * Startup succeeded, commence normal operations
  			 */
  			FatalError = false;
  			Assert(AbortStartTime == 0);
  			ReachedNormalRunning = true;
  			pmState = PM_RUN;
  
  			/*
  			 * 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 (XLogArchivingActive() && PgArchPID == 0)
  				PgArchPID = pgarch_start();
  			if (PgStatPID == 0)
  				PgStatPID = pgstat_start();
  
  			/* some workers may be scheduled to start now */
  			maybe_start_bgworker();
  
  			/* at this point we are really open for business */
  			ereport(LOG,
  				 (errmsg("database system is ready to accept connections")));
  
  			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;
  
  				/*
  				 * We can also shut down the stats collector now; there's
  				 * nothing left for it to do.
  				 */
  				if (PgStatPID != 0)
  					signal_child(PgStatPID, SIGQUIT);
  			}
  			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 (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 so, just try to start a new one; no need
  		 * to force reset of the rest of the system.  (If fail, we'll try
  		 * again in future cycles of the 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))
  				LogChildExit(LOG, _("archiver process"),
  							 pid, exitstatus);
  			if (XLogArchivingActive() && pmState == PM_RUN)
  				PgArchPID = pgarch_start();
  			continue;
  		}
  
  		/*
  		 * Was it the statistics collector?  If so, just try to start a new
  		 * one; no need to force reset of the rest of the system.  (If fail,
  		 * we'll try again in future cycles of the main loop.)
  		 */
  		if (pid == PgStatPID)
  		{
  			PgStatPID = 0;
  			if (!EXIT_STATUS_0(exitstatus))
  				LogChildExit(LOG, _("statistics collector process"),
  							 pid, exitstatus);
  			if (pmState == PM_RUN)
  				PgStatPID = pgstat_start();
  			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 */
  	PG_SETMASK(&UnBlockSig);
  
  	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_iter	iter;
  
  	slist_foreach(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, "%s: %s", _("worker process"),
  				 rw->rw_worker.bgw_name);
  
  		/* Delay restarting any bgworker that exits with a nonzero status. */
  		if (!EXIT_STATUS_0(exitstatus))
  			rw->rw_crashed_at = GetCurrentTimestamp();
  		else
  			rw->rw_crashed_at = 0;
  
  		/*
  		 * Additionally, for shared-memory-connected workers, just like a
  		 * backend, any exit status other than 0 or 1 is considered a crash
  		 * and causes a system-wide restart.
  		 */
  		if (rw->rw_worker.bgw_flags & BGWORKER_SHMEM_ACCESS)
  		{
  			if (!EXIT_STATUS_0(exitstatus) && !EXIT_STATUS_1(exitstatus))
  			{
  				rw->rw_crashed_at = GetCurrentTimestamp();
  				HandleChildCrash(pid, exitstatus, namebuf);
  				return true;
  			}
  		}
  
  		if (!ReleasePostmasterChildSlot(rw->rw_child_slot))
  		{
  			/*
  			 * Uh-oh, the child failed to clean itself up.	Treat as a crash
  			 * after all.
  			 */
  			rw->rw_crashed_at = GetCurrentTimestamp();
  			HandleChildCrash(pid, exitstatus, namebuf);
  			return true;
  		}
  
  		/* Get it out of the BackendList and clear out remaining data */
  		if (rw->rw_backend)
  		{
  			Assert(rw->rw_worker.bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION);
  			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;
  		ReportBackgroundWorkerPID(rw);		/* report child death */
  
  		LogChildExit(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, 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 signalled
  	 * 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")));
  	}
  
  	/* 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);
  			if (rw->rw_backend)
  			{
  				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
  			 * (-s 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
  			 * (-s 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;
  	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));
  	}
  
  	/* 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));
  	}
  
  	/*
  	 * Force a power-cycle of the pgarch process too.  (This isn't absolutely
  	 * necessary, but it seems like a good idea for robustness, and it
  	 * simplifies the state-machine logic in the case where a shutdown request
  	 * arrives during crash processing.)
  	 */
  	if (PgArchPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 "SIGQUIT",
  								 (int) PgArchPID)));
  		signal_child(PgArchPID, SIGQUIT);
  	}
  
  	/*
  	 * Force a power-cycle of the pgstat process too.  (This isn't absolutely
  	 * necessary, but it seems like a good idea for robustness, and it
  	 * simplifies the state-machine logic in the case where a shutdown request
  	 * arrives during crash processing.)
  	 */
  	if (PgStatPID != 0 && take_action)
  	{
  		ereport(DEBUG2,
  				(errmsg_internal("sending %s to process %d",
  								 "SIGQUIT",
  								 (int) PgStatPID)));
  		signal_child(PgStatPID, SIGQUIT);
  		allow_immediate_pgstat_restart();
  	}
  
  	/* 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_WAIT_BACKUP ||
  		pmState == PM_WAIT_READONLY ||
  		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));
  #elif defined(HAVE_DECL_SYS_SIGLIST) && HAVE_DECL_SYS_SIGLIST
  	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),
  					WTERMSIG(exitstatus) < NSIG ?
  					sys_siglist[WTERMSIG(exitstatus)] : "(unknown)"),
  	  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",
  						procname, pid, 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 (pmState == PM_WAIT_BACKUP)
  	{
  		/*
  		 * PM_WAIT_BACKUP state ends when online backup mode is not active.
  		 */
  		if (!BackupInProgress())
  			pmState = PM_WAIT_BACKENDS;
  	}
  
  	if (pmState == PM_WAIT_READONLY)
  	{
  		/*
  		 * PM_WAIT_READONLY state ends when we have no regular backends that
  		 * have been started during recovery.  We kill the startup and
  		 * walreceiver processes and transition to PM_WAIT_BACKENDS.  Ideally,
  		 * we might like to kill these processes first and then wait for
  		 * backends to die off, but that doesn't work at present because
  		 * killing the startup process doesn't release its locks.
  		 */
  		if (CountChildren(BACKEND_TYPE_NORMAL) == 0)
  		{
  			if (StartupPID != 0)
  				signal_child(StartupPID, SIGTERM);
  			if (WalReceiverPID != 0)
  				signal_child(WalReceiverPID, SIGTERM);
  			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 archiver,
  		 * stats, and syslogger processes are disregarded since
  		 * they are not connected to shared memory; we also disregard
  		 * dead_end children here. Walsenders are also disregarded,
  		 * they will be terminated later after writing the checkpoint record,
  		 * like the archiver process.
  		 */
  		if (CountChildren(BACKEND_TYPE_NORMAL | BACKEND_TYPE_WORKER) == 0 &&
  			CountUnconnectedWorkers() == 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, archiver and stats collector too */
  					SignalChildren(SIGQUIT);
  					if (PgArchPID != 0)
  						signal_child(PgArchPID, SIGQUIT);
  					if (PgStatPID != 0)
  						signal_child(PgStatPID, 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.
  		 *
  		 * Walreceiver should normally be dead by now, but not when a fast
  		 * shutdown is performed during recovery.
  		 */
  		if (PgArchPID == 0 && CountChildren(BACKEND_TYPE_ALL) == 0 &&
  			WalReceiverPID == 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 and stats
  		 * collector are 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 && PgStatPID == 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
  		{
  			/*
  			 * Terminate exclusive backup mode to avoid recovery after a clean
  			 * fast shutdown.  Since an exclusive backup can only be taken
  			 * during normal running (and not, for example, while running
  			 * under Hot Standby) it only makes sense to do this if we reached
  			 * normal running. If we're still in recovery, the backup file is
  			 * one we're recovering *from*, and we must keep it around so that
  			 * recovery restarts from the right place.
  			 */
  			if (ReachedNormalRunning)
  				CancelBackup();
  
  			/* Normal exit from the postmaster is here */
  			ExitPostmaster(0);
  		}
  	}
  
  	/*
  	 * If recovery 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 recovery fails,
  	 * because more than likely it will just fail again and we will keep
  	 * trying forever.
  	 */
  	if (pmState == PM_NO_CHILDREN && (RecoveryError || !restart_after_crash))
  		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")));
  
  		shmem_exit(1);
  		reset_shared(PostPortNumber);
  
  		StartupPID = StartupDataBase();
  		Assert(StartupPID != 0);
  		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 bgworkers that did not request backend connections
   *
   * The reason this is interesting is that workers that did request connections
   * are considered by SignalChildren; this function complements that one.
   */
  static bool
  SignalUnconnectedWorkers(int signal)
  {
  	slist_iter	iter;
  	bool		signaled = false;
  
  	slist_foreach(iter, &BackgroundWorkerList)
  	{
  		RegisteredBgWorker *rw;
  
  		rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
  
  		if (rw->rw_pid == 0)
  			continue;
  		/* ignore connected workers */
  		if (rw->rw_backend != NULL)
  			continue;
  
  		ereport(DEBUG4,
  				(errmsg_internal("sending signal %d to process %d",
  								 signal, (int) rw->rw_pid)));
  		signal_child(rw->rw_pid, signal);
  		signaled = true;
  	}
  	return signaled;
  }
  
  /*
   * 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 (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);
  	if (PgStatPID != 0)
  		signal_child(PgStatPID, signal);
  	SignalUnconnectedWorkers(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.
  	 */
  	MyCancelKey = PostmasterRandom();
  	bn->cancel_key = MyCancelKey;
  
  	/* Pass down canAcceptConnections state */
  	port->canAcceptConnections = canAcceptConnections();
  	bn->dead_end = (port->canAcceptConnections != CAC_OK &&
  					port->canAcceptConnections != CAC_WAITBACKUP);
  
  	/*
  	 * 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);
  
  		/*
  		 * Let's clean up ourselves as the postmaster child, and close the
  		 * postmaster's listen sockets.  (In EXEC_BACKEND case this is all
  		 * done in SubPostmasterMain.)
  		 */
  		IsUnderPostmaster = true;		/* we are a postmaster subprocess now */
  
  		MyProcPid = getpid();	/* reset MyProcPid */
  
  		MyStartTime = time(NULL);
  
  		/* We don't want the postmaster's proc_exit() handlers */
  		on_exit_reset();
  
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Perform additional initialization and collect startup packet */
  		BackendInitialize(port);
  
  		/* 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.
   * 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];
  	char		remote_ps_data[NI_MAXHOST];
  
  	/* Save port etc. for ps status */
  	MyProcPort = port;
  
  	/*
  	 * 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 */
  
  	/* save process start time */
  	port->SessionStartTime = GetCurrentTimestamp();
  	MyStartTime = timestamptz_to_time_t(port->SessionStartTime);
  
  	/* 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 */
  
  	/*
  	 * If possible, make this process a group leader, so that the postmaster
  	 * can signal any child processes too.	(We do this now on the off chance
  	 * that something might spawn a child process during authentication.)
  	 */
  #ifdef HAVE_SETSID
  	if (setsid() < 0)
  		elog(FATAL, "setsid() failed: %m");
  #endif
  
  	/*
  	 * We arrange for a simple exit(1) if we receive SIGTERM or SIGQUIT or
  	 * timeout while trying to collect the startup packet.	Otherwise the
  	 * postmaster cannot shutdown the database FAST or IMMED cleanly if a
  	 * buggy client fails to send the packet promptly.
  	 */
  	pqsignal(SIGTERM, startup_die);
  	pqsignal(SIGQUIT, startup_die);
  	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))));
  	if (remote_port[0] == '\0')
  		snprintf(remote_ps_data, sizeof(remote_ps_data), "%s", remote_host);
  	else
  		snprintf(remote_ps_data, sizeof(remote_ps_data), "%s(%s)", remote_host, remote_port);
  
  	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)));
  	}
  
  	/*
  	 * save remote_host and remote_port in port structure
  	 */
  	port->remote_host = strdup(remote_host);
  	port->remote_port = strdup(remote_port);
  	if (log_hostname)
  		port->remote_hostname = port->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);
  
  	/*
  	 * 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.
  	 *
  	 * For a walsender, the ps display is set in the following form:
  	 *
  	 * postgres: wal sender process <user> <host> <activity>
  	 *
  	 * To achieve that, we pass "wal sender process" as username and username
  	 * as dbname to init_ps_display(). XXX: should add a new variant of
  	 * init_ps_display() to avoid abusing the parameters like this.
  	 */
  	if (am_walsender)
  		init_ps_display("wal sender process", port->user_name, remote_ps_data,
  						update_process_title ? "authentication" : "");
  	else
  		init_ps_display(port->user_name, port->database_name, remote_ps_data,
  						update_process_title ? "authentication" : "");
  
  	/*
  	 * Disable the timeout, and prevent SIGTERM/SIGQUIT again.
  	 */
  	disable_timeout(STARTUP_PACKET_TIMEOUT, false);
  	PG_SETMASK(&BlockSig);
  }
  
  
  /*
   * BackendRun -- set up the backend's argument list and invoke PostgresMain()
   *
   * returns:
   *		Shouldn't return at all.
   *		If PostgresMain() fails, return status.
   */
  static void
  BackendRun(Port *port)
  {
  	char	  **av;
  	int			maxac;
  	int			ac;
  	long		secs;
  	int			usecs;
  	int			i;
  
  	/*
  	 * Don't want backend to be able to see the postmaster random number
  	 * generator state.  We have to clobber the static random_seed *and* start
  	 * a new random sequence in the random() library function.
  	 */
  	random_seed = 0;
  	random_start_time.tv_usec = 0;
  	/* slightly hacky way to convert timestamptz into integers */
  	TimestampDifference(0, port->SessionStartTime, &secs, &usecs);
  	srandom((unsigned int) (MyProcPid ^ (usecs << 12) ^ secs));
  
  	/*
  	 * Now, build the argv vector that will be given to PostgresMain.
  	 *
  	 * The maximum possible number of commandline arguments that could come
  	 * from ExtraOptions is (strlen(ExtraOptions) + 1) / 2; see
  	 * pg_split_opts().
  	 */
  	maxac = 2;					/* for fixed args supplied below */
  	maxac += (strlen(ExtraOptions) + 1) / 2;
  
  	av = (char **) MemoryContextAlloc(TopMemoryContext,
  									  maxac * sizeof(char *));
  	ac = 0;
  
  	av[ac++] = "postgres";
  
  	/*
  	 * Pass any backend switches specified with -o on the postmaster's own
  	 * command line.  We assume these are secure.  (It's OK to mangle
  	 * ExtraOptions now, since we're safely inside a subprocess.)
  	 */
  	pg_split_opts(av, &ac, ExtraOptions);
  
  	av[ac] = NULL;
  
  	Assert(ac < maxac);
  
  	/*
  	 * Debug: print arguments being passed to backend
  	 */
  	ereport(DEBUG3,
  			(errmsg_internal("%s child[%d]: starting with (",
  							 progname, (int) getpid())));
  	for (i = 0; i < ac; ++i)
  		ereport(DEBUG3,
  				(errmsg_internal("\t%s", av[i])));
  	ereport(DEBUG3,
  			(errmsg_internal(")")));
  
  	/*
  	 * 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(ac, av, 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
  		 */
  		mkdir(PG_TEMP_FILES_DIR, S_IRWXU);
  
  		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)
  {
  	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);
  
  	/* 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)
  	{
  		elog(LOG, "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)
  	{
  		elog(LOG, "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')
  	{
  		elog(LOG, "subprocess command line too long");
  		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))
  	{
  		elog(LOG, "CreateProcess call failed: %m (error code %lu)",
  			 GetLastError());
  		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);
  		return -1;				/* log made by save_backend_variables */
  	}
  
  	/* Drop the parameter shared memory that is now inherited to the backend */
  	if (!UnmapViewOfFile(param))
  		elog(LOG, "could not unmap view of backend parameter file: error code %lu",
  			 GetLastError());
  	if (!CloseHandle(paramHandle))
  		elog(LOG, "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.
  	 */
  	if (!pgwin32_ReserveSharedMemoryRegion(pi.hProcess))
  	{
  		/*
  		 * Failed to reserve the memory, so terminate the newly created
  		 * process and give up.
  		 */
  		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);
  		return -1;				/* logging done made by
  								 * pgwin32_ReserveSharedMemoryRegion() */
  	}
  
  	/*
  	 * 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 for 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;
  
  	/* Do this sooner rather than later... */
  	IsUnderPostmaster = true;	/* we are a postmaster subprocess now */
  
  	MyProcPid = getpid();		/* reset MyProcPid */
  
  	MyStartTime = time(NULL);
  
  	/*
  	 * make sure stderr is in binary mode before anything can possibly be
  	 * written to it, in case it's actually the syslogger pipe, so the pipe
  	 * chunking protocol isn't disturbed. Non-logpipe data gets translated on
  	 * redirection (e.g. via pg_ctl -l) anyway.
  	 */
  #ifdef WIN32
  	_setmode(fileno(stderr), _O_BINARY);
  #endif
  
  	/* Lose the postmaster's on-exit routines (really a no-op) */
  	on_exit_reset();
  
  	/* In EXEC_BACKEND case we will not have inherited these settings */
  	IsPostmasterEnvironment = true;
  	whereToSendOutput = DestNone;
  
  	/* Setup essential subsystems (to ensure elog() behaves sanely) */
  	InitializeGUCOptions();
  
  	/* Read in the variables file */
  	memset(&port, 0, sizeof(Port));
  	read_backend_variables(argv[2], &port);
  
  	/*
  	 * Set reference point for stack-depth checking
  	 */
  	set_stack_base();
  
  	/*
  	 * Set up memory area for GSS information. Mirrors the code in ConnCreate
  	 * for the non-exec case.
  	 */
  #if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
  	port.gss = (pg_gssinfo *) calloc(1, sizeof(pg_gssinfo));
  	if (!port.gss)
  		ereport(FATAL,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  #endif
  
  	/* Check we got appropriate args */
  	if (argc < 3)
  		elog(FATAL, "invalid subpostmaster invocation");
  
  	/*
  	 * 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.
  	 */
  	if (strcmp(argv[1], "--forkbackend") == 0 ||
  		strcmp(argv[1], "--forkavlauncher") == 0 ||
  		strcmp(argv[1], "--forkavworker") == 0 ||
  		strcmp(argv[1], "--forkboot") == 0 ||
  		strncmp(argv[1], "--forkbgworker=", 15) == 0)
  		PGSharedMemoryReAttach();
  
  	/* autovacuum needs this set before calling InitProcess */
  	if (strcmp(argv[1], "--forkavlauncher") == 0)
  		AutovacuumLauncherIAm();
  	if (strcmp(argv[1], "--forkavworker") == 0)
  		AutovacuumWorkerIAm();
  
  	/*
  	 * Start our win32 signal implementation. This has to be done after we
  	 * read the backend variables, because we need to pick up the signal pipe
  	 * from the parent process.
  	 */
  #ifdef WIN32
  	pgwin32_signal_initialize();
  #endif
  
  	/* In EXEC_BACKEND case we will not have inherited these settings */
  	pqinitmask();
  	PG_SETMASK(&BlockSig);
  
  	/* Read in remaining GUC variables */
  	read_nondefault_variables();
  
  	/*
  	 * 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 */
  
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/*
  		 * Need to reinitialize the SSL library in the backend, since the
  		 * context structures contain function pointers and cannot be passed
  		 * through the parameter file.
  		 *
  		 * 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)
  			secure_initialize();
  #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.  If testing EXEC_BACKEND
  		 * on Linux, you must run this as root before starting the postmaster:
  		 *
  		 * echo 0 >/proc/sys/kernel/randomize_va_space
  		 *
  		 * This prevents a randomized stack base address that causes child
  		 * shared memory to be at a different address than the parent, making
  		 * it impossible to attached to shared memory.	Return the value to
  		 * '1' when finished.
  		 */
  		CreateSharedMemoryAndSemaphores(false, 0);
  
  		/* And run the backend */
  		BackendRun(&port);		/* does not return */
  	}
  	if (strcmp(argv[1], "--forkboot") == 0)
  	{
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitAuxiliaryProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores(false, 0);
  
  		AuxiliaryProcessMain(argc - 2, argv + 2);		/* does not return */
  	}
  	if (strcmp(argv[1], "--forkavlauncher") == 0)
  	{
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores(false, 0);
  
  		AutoVacLauncherMain(argc - 2, argv + 2);		/* does not return */
  	}
  	if (strcmp(argv[1], "--forkavworker") == 0)
  	{
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores(false, 0);
  
  		AutoVacWorkerMain(argc - 2, argv + 2);	/* does not return */
  	}
  	if (strncmp(argv[1], "--forkbgworker=", 15) == 0)
  	{
  		int			shmem_slot;
  
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Restore basic shared memory pointers */
  		InitShmemAccess(UsedShmemSegAddr);
  
  		/* Need a PGPROC to run CreateSharedMemoryAndSemaphores */
  		InitProcess();
  
  		/* Attach process to shared data structures */
  		CreateSharedMemoryAndSemaphores(false, 0);
  
  		shmem_slot = atoi(argv[1] + 15);
  		MyBgworkerEntry = BackgroundWorkerEntry(shmem_slot);
  		StartBackgroundWorker();
  	}
  	if (strcmp(argv[1], "--forkarch") == 0)
  	{
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Do not want to attach to shared memory */
  
  		PgArchiverMain(argc, argv);		/* does not return */
  	}
  	if (strcmp(argv[1], "--forkcol") == 0)
  	{
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Do not want to attach to shared memory */
  
  		PgstatCollectorMain(argc, argv);		/* does not return */
  	}
  	if (strcmp(argv[1], "--forklog") == 0)
  	{
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(true);
  
  		/* 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)
  {
  	/* 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;
  	bool		start_bgworker = false;
  
  	PG_SETMASK(&BlockSig);
  
  	/* Process background worker state change. */
  	if (CheckPostmasterSignal(PMSIGNAL_BACKGROUND_WORKER_CHANGE))
  	{
  		BackgroundWorkerStateChange();
  		start_bgworker = true;
  	}
  
  	/*
  	 * 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;
  		Assert(AbortStartTime == 0);
  
  		/*
  		 * Crank up the background tasks.  It doesn't matter if this fails,
  		 * we'll just try again later.
  		 */
  		Assert(CheckpointerPID == 0);
  		CheckpointerPID = StartCheckpointer();
  		Assert(BgWriterPID == 0);
  		BgWriterPID = StartBackgroundWriter();
  
  		pmState = PM_RECOVERY;
  	}
  	if (CheckPostmasterSignal(PMSIGNAL_BEGIN_HOT_STANDBY) &&
  		pmState == PM_RECOVERY && Shutdown == NoShutdown)
  	{
  		/*
  		 * Likewise, start other special children as needed.
  		 */
  		Assert(PgStatPID == 0);
  		PgStatPID = pgstat_start();
  
  		ereport(LOG,
  		(errmsg("database system is ready to accept read only connections")));
  
  		pmState = PM_HOT_STANDBY;
  		/* Some workers may be scheduled to start now */
  		start_bgworker = true;
  	}
  
  	if (start_bgworker)
  		maybe_start_bgworker();
  
  	if (CheckPostmasterSignal(PMSIGNAL_WAKEN_ARCHIVER) &&
  		PgArchPID != 0)
  	{
  		/*
  		 * Send SIGUSR1 to archiver process, to wake it up and begin archiving
  		 * next transaction log file.
  		 */
  		signal_child(PgArchPID, SIGUSR1);
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE) &&
  		SysLoggerPID != 0)
  	{
  		/* Tell syslogger to rotate logfile */
  		signal_child(SysLoggerPID, SIGUSR1);
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_START_AUTOVAC_LAUNCHER) &&
  		Shutdown == NoShutdown)
  	{
  		/*
  		 * 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 == NoShutdown)
  	{
  		/* The autovacuum launcher wants us to start a worker process. */
  		StartAutovacuumWorker();
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_START_WALRECEIVER) &&
  		WalReceiverPID == 0 &&
  		(pmState == PM_STARTUP || pmState == PM_RECOVERY ||
  		 pmState == PM_HOT_STANDBY || pmState == PM_WAIT_READONLY) &&
  		Shutdown == NoShutdown)
  	{
  		/* Startup Process wants us to start the walreceiver process. */
  		WalReceiverPID = StartWalReceiver();
  	}
  
  	if (CheckPostmasterSignal(PMSIGNAL_ADVANCE_STATE_MACHINE) &&
  		(pmState == PM_WAIT_BACKUP || pmState == PM_WAIT_BACKENDS))
  	{
  		/* Advance postmaster's state machine */
  		PostmasterStateMachine();
  	}
  
  	if (CheckPromoteSignal() && StartupPID != 0 &&
  		(pmState == PM_STARTUP || pmState == PM_RECOVERY ||
  		 pmState == PM_HOT_STANDBY || pmState == PM_WAIT_READONLY))
  	{
  		/* Tell startup process to finish recovery */
  		signal_child(StartupPID, SIGUSR2);
  	}
  
  	PG_SETMASK(&UnBlockSig);
  
  	errno = save_errno;
  }
  
  /*
   * SIGTERM or SIGQUIT while processing startup packet.
   * Clean up and exit(1).
   *
   * XXX: possible future improvement: try to send a message indicating
   * why we are disconnecting.  Problem is to be sure we don't block while
   * doing so, nor mess up SSL initialization.  In practice, if the client
   * has wedged here, it probably couldn't do anything with the message anyway.
   */
  static void
  startup_die(SIGNAL_ARGS)
  {
  	proc_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 startup_die(), we clean up and exit(1).
   */
  static void
  StartupPacketTimeoutHandler(void)
  {
  	proc_exit(1);
  }
  
  
  /*
   * RandomSalt
   */
  static void
  RandomSalt(char *md5Salt)
  {
  	long		rand;
  
  	/*
  	 * We use % 255, sacrificing one possible byte value, so as to ensure that
  	 * all bits of the random() value participate in the result. While at it,
  	 * add one to avoid generating any null bytes.
  	 */
  	rand = PostmasterRandom();
  	md5Salt[0] = (rand % 255) + 1;
  	rand = PostmasterRandom();
  	md5Salt[1] = (rand % 255) + 1;
  	rand = PostmasterRandom();
  	md5Salt[2] = (rand % 255) + 1;
  	rand = PostmasterRandom();
  	md5Salt[3] = (rand % 255) + 1;
  }
  
  /*
   * PostmasterRandom
   */
  static long
  PostmasterRandom(void)
  {
  	/*
  	 * Select a random seed at the time of first receiving a request.
  	 */
  	if (random_seed == 0)
  	{
  		do
  		{
  			struct timeval random_stop_time;
  
  			gettimeofday(&random_stop_time, NULL);
  
  			/*
  			 * We are not sure how much precision is in tv_usec, so we swap
  			 * the high and low 16 bits of 'random_stop_time' and XOR them
  			 * with 'random_start_time'. On the off chance that the result is
  			 * 0, we loop until it isn't.
  			 */
  			random_seed = random_start_time.tv_usec ^
  				((random_stop_time.tv_usec << 16) |
  				 ((random_stop_time.tv_usec >> 16) & 0xffff));
  		}
  		while (random_seed == 0);
  
  		srandom(random_seed);
  	}
  
  	return random();
  }
  
  /*
   * Count up number of worker processes that did not request backend connections
   * See SignalUnconnectedWorkers for why this is interesting.
   */
  static int
  CountUnconnectedWorkers(void)
  {
  	slist_iter	iter;
  	int			cnt = 0;
  
  	slist_foreach(iter, &BackgroundWorkerList)
  	{
  		RegisteredBgWorker *rw;
  
  		rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
  
  		if (rw->rw_pid == 0)
  			continue;
  		/* ignore connected workers */
  		if (rw->rw_backend != NULL)
  			continue;
  
  		cnt++;
  	}
  	return cnt;
  }
  
  /*
   * Count up number of child processes of specified types (dead_end chidren
   * 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
   *
   * xlop 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;
  	char	   *av[10];
  	int			ac = 0;
  	char		typebuf[32];
  
  	/*
  	 * Set up command-line arguments for subprocess
  	 */
  	av[ac++] = "postgres";
  
  #ifdef EXEC_BACKEND
  	av[ac++] = "--forkboot";
  	av[ac++] = NULL;			/* filled in by postmaster_forkexec */
  #endif
  
  	snprintf(typebuf, sizeof(typebuf), "-x%d", type);
  	av[ac++] = typebuf;
  
  	av[ac] = NULL;
  	Assert(ac < lengthof(av));
  
  #ifdef EXEC_BACKEND
  	pid = postmaster_forkexec(ac, av);
  #else							/* !EXEC_BACKEND */
  	pid = fork_process();
  
  	if (pid == 0)				/* child */
  	{
  		IsUnderPostmaster = true;		/* we are a postmaster subprocess now */
  
  		/* Close the postmaster's sockets */
  		ClosePostmasterPorts(false);
  
  		/* Lose the postmaster's on-exit routines and port connections */
  		on_exit_reset();
  
  		/* Release postmaster's working memory context */
  		MemoryContextSwitchTo(TopMemoryContext);
  		MemoryContextDelete(PostmasterContext);
  		PostmasterContext = NULL;
  
  		AuxiliaryProcessMain(ac, av);
  		ExitPostmaster(0);
  	}
  #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 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() == CAC_OK)
  	{
  		bn = (Backend *) malloc(sizeof(Backend));
  		if (bn)
  		{
  			/*
  			 * 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.
  			 */
  			MyCancelKey = PostmasterRandom();
  			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 signalling in
  	 * quick succession between the autovac launcher and postmaster in case
  	 * things get ugly.
  	 */
  	if (AutoVacPID != 0)
  	{
  		AutoVacWorkerFailed();
  		avlauncher_needs_signal = true;
  	}
  }
  
  /*
   * 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)
  	{
  		elog(LOG, "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))
  	{
  		elog(LOG, "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_worker_processes);
  }
  
  /*
   * Connect background worker to a database.
   */
  void
  BackgroundWorkerInitializeConnection(char *dbname, char *username)
  {
  	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, NULL);
  
  	/* 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.
   *
   * This code is heavily based on autovacuum.c, q.v.
   */
  static void
  do_start_bgworker(RegisteredBgWorker *rw)
  {
  	pid_t		worker_pid;
  
  	ereport(LOG,
  			(errmsg("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:
  			ereport(LOG,
  					(errmsg("could not fork worker process: %m")));
  			return;
  
  #ifndef EXEC_BACKEND
  		case 0:
  			/* in postmaster child ... */
  			/* Close the postmaster's sockets */
  			ClosePostmasterPorts(false);
  
  			/* Lose the postmaster's on-exit routines */
  			on_exit_reset();
  
  			/* Do NOT release postmaster's working memory context */
  
  			MyBgworkerEntry = &rw->rw_worker;
  			StartBackgroundWorker();
  			break;
  #endif
  		default:
  			rw->rw_pid = worker_pid;
  			if (rw->rw_backend)
  				rw->rw_backend->pid = rw->rw_pid;
  			ReportBackgroundWorkerPID(rw);
  	}
  }
  
  /*
   * 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_WAIT_READONLY:
  		case PM_WAIT_BACKUP:
  			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.
   *
   * Some info from the Backend is copied into the passed rw.
   */
  static bool
  assign_backendlist_entry(RegisteredBgWorker *rw)
  {
  	Backend    *bn = malloc(sizeof(Backend));
  
  	if (bn == NULL)
  	{
  		ereport(LOG,
  				(errcode(ERRCODE_OUT_OF_MEMORY),
  				 errmsg("out of memory")));
  
  		/*
  		 * The worker didn't really crash, but setting this nonzero makes
  		 * postmaster wait a bit before attempting to start it again; if it
  		 * tried again right away, most likely it'd find itself under the same
  		 * memory pressure.
  		 */
  		rw->rw_crashed_at = GetCurrentTimestamp();
  		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.
  	 */
  	MyCancelKey = PostmasterRandom();
  	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 one background worker.
   *
   * As a side effect, the bgworker control variables are set or reset whenever
   * there are more workers to start after this one, and whenever the overall
   * system state requires it.
   */
  static void
  maybe_start_bgworker(void)
  {
  	slist_mutable_iter	iter;
  	TimestampTz now = 0;
  
  	if (FatalError)
  	{
  		StartWorkerNeeded = false;
  		HaveCrashedWorker = false;
  		return;					/* not yet */
  	}
  
  	HaveCrashedWorker = false;
  
  	slist_foreach_modify(iter, &BackgroundWorkerList)
  	{
  		RegisteredBgWorker *rw;
  
  		rw = slist_container(RegisteredBgWorker, rw_lnode, iter.cur);
  
  		/* already running? */
  		if (rw->rw_pid != 0)
  			continue;
  
  		/* marked for death? */
  		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)
  			{
  				ForgetBackgroundWorker(&iter);
  				continue;
  			}
  
  			if (now == 0)
  				now = GetCurrentTimestamp();
  
  			if (!TimestampDifferenceExceeds(rw->rw_crashed_at, now,
  									  rw->rw_worker.bgw_restart_time * 1000))
  			{
  				HaveCrashedWorker = true;
  				continue;
  			}
  		}
  
  		if (bgworker_should_start_now(rw->rw_worker.bgw_start_time))
  		{
  			/* reset crash time before calling assign_backendlist_entry */
  			rw->rw_crashed_at = 0;
  
  			/*
  			 * If necessary, allocate and assign the Backend element.  Note we
  			 * must do this before forking, so that we can handle out of
  			 * memory properly.
  			 *
  			 * If not connected, we don't need a Backend element, but we still
  			 * need a PMChildSlot.
  			 */
  			if (rw->rw_worker.bgw_flags & BGWORKER_BACKEND_DATABASE_CONNECTION)
  			{
  				if (!assign_backendlist_entry(rw))
  					return;
  			}
  			else
  				rw->rw_child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
  
  			do_start_bgworker(rw); /* sets rw->rw_pid */
  
  			if (rw->rw_backend)
  			{
  				dlist_push_head(&BackendList, &rw->rw_backend->elem);
  #ifdef EXEC_BACKEND
  				ShmemBackendArrayAdd(rw->rw_backend);
  #endif
  			}
  
  			/*
  			 * Have ServerLoop call us again.  Note that there might not
  			 * actually *be* another runnable worker, but we don't care all
  			 * that much; we will find out the next time we run.
  			 */
  			StartWorkerNeeded = true;
  			return;
  		}
  	}
  
  	/* no runnable worker found */
  	StartWorkerNeeded = false;
  }
  
  /*
   * 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 pgsocket pgStatSock;
  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;
  
  	param->UsedShmemSegID = UsedShmemSegID;
  	param->UsedShmemSegAddr = UsedShmemSegAddr;
  
  	param->ShmemLock = ShmemLock;
  	param->ShmemVariableCache = ShmemVariableCache;
  	param->ShmemBackendArray = ShmemBackendArray;
  
  #ifndef HAVE_SPINLOCKS
  	param->SpinlockSemaArray = SpinlockSemaArray;
  #endif
  	param->MainLWLockArray = MainLWLockArray;
  	param->ProcStructLock = ProcStructLock;
  	param->ProcGlobal = ProcGlobal;
  	param->AuxiliaryProcs = AuxiliaryProcs;
  	param->PreparedXactProcs = PreparedXactProcs;
  	param->PMSignalState = PMSignalState;
  	if (!write_inheritable_socket(&param->pgStatSock, pgStatSock, childPid))
  		return false;
  
  	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->max_safe_fds = max_safe_fds;
  
  	param->MaxBackends = MaxBackends;
  
  #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);
  
  	strlcpy(param->ExtraOptions, ExtraOptions, 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 read from 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;
  
  	UsedShmemSegID = param->UsedShmemSegID;
  	UsedShmemSegAddr = param->UsedShmemSegAddr;
  
  	ShmemLock = param->ShmemLock;
  	ShmemVariableCache = param->ShmemVariableCache;
  	ShmemBackendArray = param->ShmemBackendArray;
  
  #ifndef HAVE_SPINLOCKS
  	SpinlockSemaArray = param->SpinlockSemaArray;
  #endif
  	MainLWLockArray = param->MainLWLockArray;
  	ProcStructLock = param->ProcStructLock;
  	ProcGlobal = param->ProcGlobal;
  	AuxiliaryProcs = param->AuxiliaryProcs;
  	PreparedXactProcs = param->PreparedXactProcs;
  	PMSignalState = param->PMSignalState;
  	read_inheritable_socket(&pgStatSock, &param->pgStatSock);
  
  	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;
  	max_safe_fds = param->max_safe_fds;
  
  	MaxBackends = 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);
  
  	strlcpy(ExtraOptions, param->ExtraOptions, MAXPGPATH);
  }
  
  
  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))
  		ereport(FATAL,
  				(errcode_for_file_access(),
  				 errmsg_internal("could not create pipe to monitor postmaster death: %m")));
  
  	/*
  	 * 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))
  		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 */
  }
  