src/pulsecore/semaphore-posix.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2006 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 <errno.h>
  27 #include <pthread.h>
  28 #include <semaphore.h>
  29
  30 #include <pulse/xmalloc.h>
  31 #include <pulsecore/macro.h>
  32
  33 #include "semaphore.h"
  34
  35 struct pa_semaphore {
  36     sem_t sem;
  37 };
  38
  39 pa_semaphore* pa_semaphore_new(unsigned value) {
  40     pa_semaphore *s;
  41
  42     s = pa_xnew(pa_semaphore, 1);
  43     pa_assert_se(sem_init(&s->sem, 0, value) == 0);
  44     return s;
  45 }
  46
  47 void pa_semaphore_free(pa_semaphore *s) {
  48     pa_assert(s);
  49     pa_assert_se(sem_destroy(&s->sem) == 0);
  50     pa_xfree(s);
  51 }
  52
  53 void pa_semaphore_post(pa_semaphore *s) {
  54     pa_assert(s);
  55     pa_assert_se(sem_post(&s->sem) == 0);
  56 }
  57
  58 void pa_semaphore_wait(pa_semaphore *s) {
  59     int ret;
  60     pa_assert(s);
  61
  62     do {
  63         ret = sem_wait(&s->sem);
  64     } while (ret < 0 && errno == EINTR);
  65
  66     pa_assert(ret == 0);
  67 }
  68
  69 pa_semaphore* pa_static_semaphore_get(pa_static_semaphore *s, unsigned value) {
  70     pa_semaphore *m;
  71
  72     pa_assert(s);
  73
  74     /* First, check if already initialized and short cut */
  75     if ((m = pa_atomic_ptr_load(&s->ptr)))
  76         return m;
  77
  78     /* OK, not initialized, so let's allocate, and fill in */
  79     m = pa_semaphore_new(value);
  80     if ((pa_atomic_ptr_cmpxchg(&s->ptr, NULL, m)))
  81         return m;
  82
  83     pa_semaphore_free(m);
  84
  85     /* Him, filling in failed, so someone else must have filled in
  86      * already */
  87     pa_assert_se(m = pa_atomic_ptr_load(&s->ptr));
  88     return m;
  89 }