code.delx.au - pulseaudio/blob - src/pulsecore/fdsem.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of PulseAudio.
   5
   6   Copyright 2006 Lennart Poettering
   7
   8   PulseAudio is free software; you can redistribute it and/or modify
   9   it under the terms of the GNU Lesser General Public License as
  10   published by the Free Software Foundation; either version 2.1 of the
  11   License, or (at your option) any later version.
  12
  13   PulseAudio is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public
  19   License along with PulseAudio; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  21   USA.
  22 ***/
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include <config.h>
  26 #endif
  27
  28 #include <unistd.h>
  29 #include <errno.h>
  30
  31 #include <pulsecore/atomic.h>
  32 #include <pulsecore/log.h>
  33 #include <pulsecore/thread.h>
  34 #include <pulsecore/macro.h>
  35 #include <pulsecore/core-util.h>
  36 #include <pulse/xmalloc.h>
  37
  38 #include "fdsem.h"
  39
  40 struct pa_fdsem {
  41     int fds[2];
  42     pa_atomic_t waiting;
  43     pa_atomic_t signalled;
  44     pa_atomic_t in_pipe;
  45 };
  46
  47 pa_fdsem *pa_fdsem_new(void) {
  48     pa_fdsem *f;
  49
  50     f = pa_xnew(pa_fdsem, 1);
  51
  52     if (pipe(f->fds) < 0) {
  53         pa_xfree(f);
  54         return NULL;
  55     }
  56
  57     pa_make_fd_cloexec(f->fds[0]);
  58     pa_make_fd_cloexec(f->fds[1]);
  59
  60     pa_atomic_store(&f->waiting, 0);
  61     pa_atomic_store(&f->signalled, 0);
  62     pa_atomic_store(&f->in_pipe, 0);
  63
  64     return f;
  65 }
  66
  67 void pa_fdsem_free(pa_fdsem *f) {
  68     pa_assert(f);
  69
  70     pa_close_pipe(f->fds);
  71
  72     pa_xfree(f);
  73 }
  74
  75 static void flush(pa_fdsem *f) {
  76     ssize_t r;
  77     pa_assert(f);
  78
  79     if (pa_atomic_load(&f->in_pipe) <= 0)
  80         return;
  81
  82     do {
  83         char x[10];
  84
  85         if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) {
  86             pa_assert(r < 0 && errno == EINTR);
  87             continue;
  88         }
  89
  90     } while (pa_atomic_sub(&f->in_pipe, r) > r);
  91 }
  92
  93 void pa_fdsem_post(pa_fdsem *f) {
  94     pa_assert(f);
  95
  96     if (pa_atomic_cmpxchg(&f->signalled, 0, 1)) {
  97
  98         if (pa_atomic_load(&f->waiting)) {
  99             ssize_t r;
 100             char x = 'x';
 101
 102             pa_atomic_inc(&f->in_pipe);
 103
 104             for (;;) {
 105
 106                 if ((r = write(f->fds[1], &x, 1)) != 1) {
 107                     pa_assert(r < 0 && errno == EINTR);
 108                     continue;
 109                 }
 110
 111                 break;
 112             }
 113         }
 114     }
 115 }
 116
 117 void pa_fdsem_wait(pa_fdsem *f) {
 118     pa_assert(f);
 119
 120     flush(f);
 121
 122     if (pa_atomic_cmpxchg(&f->signalled, 1, 0))
 123         return;
 124
 125     pa_atomic_inc(&f->waiting);
 126
 127     while (!pa_atomic_cmpxchg(&f->signalled, 1, 0)) {
 128         char x[10];
 129         ssize_t r;
 130
 131         if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) {
 132             pa_assert(r < 0 && errno == EINTR);
 133             continue;
 134         }
 135
 136         pa_atomic_sub(&f->in_pipe, r);
 137     }
 138
 139     pa_assert_se(pa_atomic_dec(&f->waiting) >= 1);
 140 }
 141
 142 int pa_fdsem_try(pa_fdsem *f) {
 143     pa_assert(f);
 144
 145     flush(f);
 146
 147     if (pa_atomic_cmpxchg(&f->signalled, 1, 0))
 148         return 1;
 149
 150     return 0;
 151 }
 152
 153
 154 int pa_fdsem_get(pa_fdsem *f) {
 155     pa_assert(f);
 156
 157     return f->fds[0];
 158 }
 159
 160 int pa_fdsem_before_poll(pa_fdsem *f) {
 161     pa_assert(f);
 162
 163     flush(f);
 164
 165     if (pa_atomic_cmpxchg(&f->signalled, 1, 0))
 166         return -1;
 167
 168     pa_atomic_inc(&f->waiting);
 169
 170     if (pa_atomic_cmpxchg(&f->signalled, 1, 0)) {
 171         pa_assert_se(pa_atomic_dec(&f->waiting) >= 1);
 172         return -1;
 173     }
 174     return 0;
 175 }
 176
 177 int pa_fdsem_after_poll(pa_fdsem *f) {
 178     pa_assert(f);
 179
 180     pa_assert_se(pa_atomic_dec(&f->waiting) >= 1);
 181
 182     flush(f);
 183
 184     if (pa_atomic_cmpxchg(&f->signalled, 1, 0))
 185         return 1;
 186
 187     return 0;
 188 }