postgresql/src/backend/postmaster/fork_process.c

/*
 * fork_process.c
 *   A simple wrapper on top of fork(). This does not handle the
 *   EXEC_BACKEND case; it might be extended to do so, but it would be
 *   considerably more complex.
 *
 * Copyright (c) 1996-2005, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/postmaster/fork_process.c,v 1.2 2005/03/13 23:27:38 tgl Exp $
 */
#include "postgres.h"
#include "postmaster/fork_process.h"

#include <time.h>
#include <sys/time.h>
#include <unistd.h>

/*
 * Wrapper for fork(). Return values are the same as those for fork():
 * -1 if the fork failed, 0 in the child process, and the PID of the
 * child in the parent process.
 */
pid_t
fork_process(void)
{
	pid_t result;
#ifdef LINUX_PROFILE
	struct itimerval prof_itimer;
#endif

	/*
	 * Flush stdio channels just before fork, to avoid double-output
	 * problems. Ideally we'd use fflush(NULL) here, but there are still a
	 * few non-ANSI stdio libraries out there (like SunOS 4.1.x) that
	 * coredump if we do. Presently stdout and stderr are the only stdio
	 * output channels used by the postmaster, so fflush'ing them should
	 * be sufficient.
	 */
	fflush(stdout);
	fflush(stderr);

#ifdef LINUX_PROFILE
	/*
	 * Linux's fork() resets the profiling timer in the child process. If
	 * we want to profile child processes then we need to save and restore
	 * the timer setting.  This is a waste of time if not profiling,
	 * however, so only do it if commanded by specific -DLINUX_PROFILE
	 * switch.
	 */
	getitimer(ITIMER_PROF, &prof_itimer);
#endif

#ifdef __BEOS__
	/* Specific beos actions before backend startup */
	beos_before_backend_startup();
#endif

	result = fork();
	if (result == (pid_t) -1)
	{
		/* fork failed */
#ifdef __BEOS__
		/* Specific beos backend startup actions */
		beos_backend_startup_failed();
#endif
	}
	else if (result == 0)
	{
		/* fork succeeded, in child */
#ifdef LINUX_PROFILE
		setitimer(ITIMER_PROF, &prof_itimer, NULL);
#endif

#ifdef __BEOS__
		/* Specific beos backend startup actions */
		beos_backend_startup();
#endif
	}

	return result;
}