src/backend/postmaster/fork_process.c

   1 /*
   2  * fork_process.c
   3  *       A simple wrapper on top of fork(). This does not handle the
   4  *       EXEC_BACKEND case; it might be extended to do so, but it would be
   5  *       considerably more complex.
   6  *
   7  * Copyright (c) 1996-2007, PostgreSQL Global Development Group
   8  *
   9  * IDENTIFICATION
  10  *        $PostgreSQL$
  11  */
  12 #include "postgres.h"
  13 #include "postmaster/fork_process.h"
  14
  15 #include <time.h>
  16 #include <sys/time.h>
  17 #include <unistd.h>
  18
  19 #ifndef WIN32
  20 /*
  21  * Wrapper for fork(). Return values are the same as those for fork():
  22  * -1 if the fork failed, 0 in the child process, and the PID of the
  23  * child in the parent process.
  24  */
  25 pid_t
  26 fork_process(void)
  27 {
  28         pid_t           result;
  29
  30 #ifdef LINUX_PROFILE
  31         struct itimerval prof_itimer;
  32 #endif
  33
  34         /*
  35          * Flush stdio channels just before fork, to avoid double-output problems.
  36          * Ideally we'd use fflush(NULL) here, but there are still a few non-ANSI
  37          * stdio libraries out there (like SunOS 4.1.x) that coredump if we do.
  38          * Presently stdout and stderr are the only stdio output channels used by
  39          * the postmaster, so fflush'ing them should be sufficient.
  40          */
  41         fflush(stdout);
  42         fflush(stderr);
  43
  44 #ifdef LINUX_PROFILE
  45
  46         /*
  47          * Linux's fork() resets the profiling timer in the child process. If we
  48          * want to profile child processes then we need to save and restore the
  49          * timer setting.  This is a waste of time if not profiling, however, so
  50          * only do it if commanded by specific -DLINUX_PROFILE switch.
  51          */
  52         getitimer(ITIMER_PROF, &prof_itimer);
  53 #endif
  54
  55         result = fork();
  56         if (result == 0)
  57         {
  58                 /* fork succeeded, in child */
  59 #ifdef LINUX_PROFILE
  60                 setitimer(ITIMER_PROF, &prof_itimer, NULL);
  61 #endif
  62
  63         }
  64
  65         return result;
  66 }
  67
  68 #endif   /* ! WIN32 */