code.delx.au - pulseaudio/blob - src/pulse/fork-detect.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2009 Lennart Poettering
   5
   6   PulseAudio is free software; you can redistribute it and/or modify
   7   it under the terms of the GNU Lesser General Public License as published
   8   by the Free Software Foundation; either version 2.1 of the License,
   9   or (at your option) any later version.
  10
  11   PulseAudio is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with PulseAudio; if not, write to the Free Software
  18   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  19   USA.
  20 ***/
  21
  22 #ifdef HAVE_CONFIG_H
  23 #include <config.h>
  24 #endif
  25
  26 #include <unistd.h>
  27
  28 #include <pulsecore/atomic.h>
  29 #include <pulsecore/macro.h>
  30
  31 #include "fork-detect.h"
  32
  33 int pa_detect_fork(void) {
  34     static pa_atomic_t pid = PA_ATOMIC_INIT((int) -1);
  35
  36     /* Some really stupid applications (Hey, vim, that means you!)
  37      * love to fork after initializing
  38      * gtk/libcanberra/pulseaudio. This is really bad style. We
  39      * however have to deal with this cleanly, so we try to detect the
  40      * forks making sure all our calls fail cleanly after the fork. */
  41
  42     pa_assert(sizeof(pa_atomic_t) >= sizeof(pid_t));
  43
  44     for (;;) {
  45         pid_t stored_pid = (pid_t) pa_atomic_load(&pid);
  46
  47         /* First let's check whether the current pid matches the stored one */
  48         if (stored_pid == getpid())
  49             return FALSE;
  50
  51         /* Does it contain a different PID than ours? Then the process got forked. */
  52         if ((int) stored_pid != (int) -1)
  53             return TRUE;
  54
  55         /* Ok, it still contains no PID, then store it */
  56         if (pa_atomic_cmpxchg(&pid, (int) -1, (int) getpid()))
  57             return FALSE;
  58     }
  59 }