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       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                 :          0 : 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_cc(sizeof(pa_atomic_t) >= sizeof(pid_t));
      43                 :            : 
      44                 :            :     for (;;) {
      45                 :          0 :         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         [ #  # ]:          0 :         if (stored_pid == getpid())
      49                 :            :             return FALSE;
      50                 :            : 
      51                 :            :         /* Does it contain a different PID than ours? Then the process got forked. */
      52         [ #  # ]:          0 :         if ((int) stored_pid != (int) -1)
      53                 :            :             return TRUE;
      54                 :            : 
      55                 :            :         /* Ok, it still contains no PID, then store it */
      56         [ #  # ]:          0 :         if (pa_atomic_cmpxchg(&pid, (int) -1, (int) getpid()))
      57                 :            :             return FALSE;
      58                 :            :     }
      59                 :            : }