text: /*-------------------------------------------------------------------------
   *
   * startup.c
   *
   * The Startup process initialises the server and performs any recovery
   * actions that have been specified. Notice that there is no "main loop"
   * since the Startup process ends as soon as initialisation is complete.
   * (in standby mode, one can think of the replay loop as a main loop,
   * though.)
   *
   *
   * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
   *
   *
   * IDENTIFICATION
   *	  src/backend/postmaster/startup.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include <signal.h>
  #include <unistd.h>
  
  #include "access/xlog.h"
  #include "libpq/pqsignal.h"
  #include "miscadmin.h"
  #include "postmaster/startup.h"
  #include "storage/ipc.h"
  #include "storage/latch.h"
  #include "storage/pmsignal.h"
  #include "storage/standby.h"
  #include "utils/guc.h"
  #include "utils/timeout.h"
  
  
  /*
   * Flags set by interrupt handlers for later service in the redo loop.
   */
  static volatile sig_atomic_t got_SIGHUP = false;
  static volatile sig_atomic_t shutdown_requested = false;
  static volatile sig_atomic_t promote_triggered = false;
  
  /*
   * Flag set when executing a restore command, to tell SIGTERM signal handler
   * that it's safe to just proc_exit.
   */
  static volatile sig_atomic_t in_restore_command = false;
  
  /* Signal handlers */
  static void startupproc_quickdie(SIGNAL_ARGS);
  static void StartupProcSigUsr1Handler(SIGNAL_ARGS);
  static void StartupProcTriggerHandler(SIGNAL_ARGS);
  static void StartupProcSigHupHandler(SIGNAL_ARGS);
  
  
  /* --------------------------------
   *		signal handler routines
   * --------------------------------
   */
  
  /*
   * startupproc_quickdie() occurs when signalled SIGQUIT by the postmaster.
   *
   * Some backend has bought the farm,
   * so we need to stop what we're doing and exit.
   */
  static void
  startupproc_quickdie(SIGNAL_ARGS)
  {
  	/*
  	 * We DO NOT want to run proc_exit() or atexit() callbacks -- we're here
  	 * because shared memory may be corrupted, so we don't want to try to
  	 * clean up our transaction.  Just nail the windows shut and get out of
  	 * town.  The callbacks wouldn't be safe to run from a signal handler,
  	 * anyway.
  	 *
  	 * Note we do _exit(2) not _exit(0).  This is to force the postmaster into
  	 * a system reset cycle if someone sends a manual SIGQUIT to a random
  	 * backend.  This is necessary precisely because we don't clean up our
  	 * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
  	 * should ensure the postmaster sees this as a crash, too, but no harm in
  	 * being doubly sure.)
  	 */
  	_exit(2);
  }
  
  
  /* SIGUSR1: let latch facility handle the signal */
  static void
  StartupProcSigUsr1Handler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	latch_sigusr1_handler();
  
  	errno = save_errno;
  }
  
  /* SIGUSR2: set flag to finish recovery */
  static void
  StartupProcTriggerHandler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	promote_triggered = true;
  	WakeupRecovery();
  
  	errno = save_errno;
  }
  
  /* SIGHUP: set flag to re-read config file at next convenient time */
  static void
  StartupProcSigHupHandler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	got_SIGHUP = true;
  	WakeupRecovery();
  
  	errno = save_errno;
  }
  
  /* SIGTERM: set flag to abort redo and exit */
  static void
  StartupProcShutdownHandler(SIGNAL_ARGS)
  {
  	int			save_errno = errno;
  
  	if (in_restore_command)
  		proc_exit(1);
  	else
  		shutdown_requested = true;
  	WakeupRecovery();
  
  	errno = save_errno;
  }
  
  /* Handle SIGHUP and SIGTERM signals of startup process */
  void
  HandleStartupProcInterrupts(void)
  {
  	/*
  	 * Check if we were requested to re-read config file.
  	 */
  	if (got_SIGHUP)
  	{
  		got_SIGHUP = false;
  		ProcessConfigFile(PGC_SIGHUP);
  	}
  
  	/*
  	 * Check if we were requested to exit without finishing recovery.
  	 */
  	if (shutdown_requested)
  		proc_exit(1);
  
  	/*
  	 * Emergency bailout if postmaster has died.  This is to avoid the
  	 * necessity for manual cleanup of all postmaster children.
  	 */
  	if (IsUnderPostmaster && !PostmasterIsAlive())
  		exit(1);
  }
  
  
  /* ----------------------------------
   *	Startup Process main entry point
   * ----------------------------------
   */
  void
  StartupProcessMain(void)
  {
  	/*
  	 * If possible, make this process a group leader, so that the postmaster
  	 * can signal any child processes too.
  	 */
  #ifdef HAVE_SETSID
  	if (setsid() < 0)
  		elog(FATAL, "setsid() failed: %m");
  #endif
  
  	/*
  	 * Properly accept or ignore signals the postmaster might send us.
  	 */
  	pqsignal(SIGHUP, StartupProcSigHupHandler); /* reload config file */
  	pqsignal(SIGINT, SIG_IGN);	/* ignore query cancel */
  	pqsignal(SIGTERM, StartupProcShutdownHandler);		/* request shutdown */
  	pqsignal(SIGQUIT, startupproc_quickdie);	/* hard crash time */
  	InitializeTimeouts();		/* establishes SIGALRM handler */
  	pqsignal(SIGPIPE, SIG_IGN);
  	pqsignal(SIGUSR1, StartupProcSigUsr1Handler);
  	pqsignal(SIGUSR2, StartupProcTriggerHandler);
  
  	/*
  	 * Reset some signals that are accepted by postmaster but not here
  	 */
  	pqsignal(SIGCHLD, SIG_DFL);
  	pqsignal(SIGTTIN, SIG_DFL);
  	pqsignal(SIGTTOU, SIG_DFL);
  	pqsignal(SIGCONT, SIG_DFL);
  	pqsignal(SIGWINCH, SIG_DFL);
  
  	/*
  	 * Register timeouts needed for standby mode
  	 */
  	RegisterTimeout(STANDBY_DEADLOCK_TIMEOUT, StandbyDeadLockHandler);
  	RegisterTimeout(STANDBY_TIMEOUT, StandbyTimeoutHandler);
  
  	/*
  	 * Unblock signals (they were blocked when the postmaster forked us)
  	 */
  	PG_SETMASK(&UnBlockSig);
  
  	/*
  	 * Do what we came for.
  	 */
  	StartupXLOG();
  
  	/*
  	 * Exit normally. Exit code 0 tells postmaster that we completed recovery
  	 * successfully.
  	 */
  	proc_exit(0);
  }
  
  void
  PreRestoreCommand(void)
  {
  	/*
  	 * Set in_restore_command to tell the signal handler that we should exit
  	 * right away on SIGTERM. We know that we're at a safe point to do that.
  	 * Check if we had already received the signal, so that we don't miss a
  	 * shutdown request received just before this.
  	 */
  	in_restore_command = true;
  	if (shutdown_requested)
  		proc_exit(1);
  }
  
  void
  PostRestoreCommand(void)
  {
  	in_restore_command = false;
  }
  
  bool
  IsPromoteTriggered(void)
  {
  	return promote_triggered;
  }
  
  void
  ResetPromoteTriggered(void)
  {
  	promote_triggered = false;
  }
  