src/pulsecore/fdsem.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
   8   published by the Free Software Foundation; either version 2.1 of the
   9   License, 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   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public
  17   License 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 #ifdef HAVE_SYS_SYSCALL_H
  27 #include <sys/syscall.h>
  28 #endif
  29
  30 #include <unistd.h>
  31 #include <errno.h>
  32
  33 #include <pulsecore/atomic.h>
  34 #include <pulsecore/log.h>
  35 #include <pulsecore/thread.h>
  36 #include <pulsecore/macro.h>
  37 #include <pulsecore/core-util.h>
  38 #include <pulse/xmalloc.h>
  39
  40 #ifndef HAVE_PIPE
  41 #include <pulsecore/pipe.h>
  42 #endif
  43
  44 #ifdef HAVE_SYS_EVENTFD_H
  45 #include <sys/eventfd.h>
  46 #endif
  47
  48 #include "fdsem.h"
  49
  50 struct pa_fdsem {
  51     int fds[2];
  52 #ifdef HAVE_SYS_EVENTFD_H
  53     int efd;
  54 #endif
  55
  56     pa_fdsem_data *data;
  57 };
  58
  59 pa_fdsem *pa_fdsem_new(void) {
  60     pa_fdsem *f;
  61
  62     f = pa_xmalloc(PA_ALIGN(sizeof(pa_fdsem)) + PA_ALIGN(sizeof(pa_fdsem_data)));
  63
  64 #ifdef HAVE_SYS_EVENTFD_H
  65     if ((f->efd = eventfd(0, 0)) >= 0) {
  66         pa_make_fd_cloexec(f->efd);
  67         f->fds[0] = f->fds[1] = -1;
  68     } else
  69 #endif
  70     {
  71         if (pipe(f->fds) < 0) {
  72             pa_xfree(f);
  73             return NULL;
  74         }
  75
  76         pa_make_fd_cloexec(f->fds[0]);
  77         pa_make_fd_cloexec(f->fds[1]);
  78     }
  79
  80     f->data = (pa_fdsem_data*) ((uint8_t*) f + PA_ALIGN(sizeof(pa_fdsem)));
  81
  82     pa_atomic_store(&f->data->waiting, 0);
  83     pa_atomic_store(&f->data->signalled, 0);
  84     pa_atomic_store(&f->data->in_pipe, 0);
  85
  86     return f;
  87 }
  88
  89 pa_fdsem *pa_fdsem_open_shm(pa_fdsem_data *data, int event_fd) {
  90     pa_fdsem *f = NULL;
  91
  92     pa_assert(data);
  93     pa_assert(event_fd >= 0);
  94
  95 #ifdef HAVE_SYS_EVENTFD_H
  96     f = pa_xnew(pa_fdsem, 1);
  97
  98     f->efd = event_fd;
  99     pa_make_fd_cloexec(f->efd);
 100     f->fds[0] = f->fds[1] = -1;
 101     f->data = data;
 102 #endif
 103
 104     return f;
 105 }
 106
 107 pa_fdsem *pa_fdsem_new_shm(pa_fdsem_data *data, int* event_fd) {
 108     pa_fdsem *f = NULL;
 109
 110     pa_assert(data);
 111     pa_assert(event_fd);
 112
 113 #ifdef HAVE_SYS_EVENTFD_H
 114
 115     f = pa_xnew(pa_fdsem, 1);
 116
 117     if ((f->efd = eventfd(0, 0)) < 0) {
 118         pa_xfree(f);
 119         return NULL;
 120     }
 121
 122     pa_make_fd_cloexec(f->efd);
 123     f->fds[0] = f->fds[1] = -1;
 124     f->data = data;
 125
 126     pa_atomic_store(&f->data->waiting, 0);
 127     pa_atomic_store(&f->data->signalled, 0);
 128     pa_atomic_store(&f->data->in_pipe, 0);
 129
 130 #endif
 131
 132     return f;
 133 }
 134
 135 void pa_fdsem_free(pa_fdsem *f) {
 136     pa_assert(f);
 137
 138 #ifdef HAVE_SYS_EVENTFD_H
 139     if (f->efd >= 0)
 140         pa_close(f->efd);
 141 #endif
 142     pa_close_pipe(f->fds);
 143
 144     pa_xfree(f);
 145 }
 146
 147 static void flush(pa_fdsem *f) {
 148     ssize_t r;
 149     pa_assert(f);
 150
 151     if (pa_atomic_load(&f->data->in_pipe) <= 0)
 152         return;
 153
 154     do {
 155         char x[10];
 156
 157 #ifdef HAVE_SYS_EVENTFD_H
 158         if (f->efd >= 0) {
 159             uint64_t u;
 160
 161             if ((r = read(f->efd, &u, sizeof(u))) != sizeof(u)) {
 162                 pa_assert(r < 0 && errno == EINTR);
 163                 continue;
 164             }
 165             r = (ssize_t) u;
 166         } else
 167 #endif
 168
 169         if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) {
 170             pa_assert(r < 0 && errno == EINTR);
 171             continue;
 172         }
 173
 174     } while (pa_atomic_sub(&f->data->in_pipe, (int) r) > (int) r);
 175 }
 176
 177 void pa_fdsem_post(pa_fdsem *f) {
 178     pa_assert(f);
 179
 180     if (pa_atomic_cmpxchg(&f->data->signalled, 0, 1)) {
 181
 182         if (pa_atomic_load(&f->data->waiting)) {
 183             ssize_t r;
 184             char x = 'x';
 185
 186             pa_atomic_inc(&f->data->in_pipe);
 187
 188             for (;;) {
 189
 190 #ifdef HAVE_SYS_EVENTFD_H
 191                 if (f->efd >= 0) {
 192                     uint64_t u = 1;
 193
 194                     if ((r = write(f->efd, &u, sizeof(u))) != sizeof(u)) {
 195                         pa_assert(r < 0 && errno == EINTR);
 196                         continue;
 197                     }
 198                 } else
 199 #endif
 200
 201                 if ((r = write(f->fds[1], &x, 1)) != 1) {
 202                     pa_assert(r < 0 && errno == EINTR);
 203                     continue;
 204                 }
 205
 206                 break;
 207             }
 208         }
 209     }
 210 }
 211
 212 void pa_fdsem_wait(pa_fdsem *f) {
 213     pa_assert(f);
 214
 215     flush(f);
 216
 217     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 218         return;
 219
 220     pa_atomic_inc(&f->data->waiting);
 221
 222     while (!pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
 223         char x[10];
 224         ssize_t r;
 225
 226 #ifdef HAVE_SYS_EVENTFD_H
 227         if (f->efd >= 0) {
 228             uint64_t u;
 229
 230             if ((r = read(f->efd, &u, sizeof(u))) != sizeof(u)) {
 231                 pa_assert(r < 0 && errno == EINTR);
 232                 continue;
 233             }
 234
 235             r = (ssize_t) u;
 236         } else
 237 #endif
 238
 239         if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) {
 240             pa_assert(r < 0 && errno == EINTR);
 241             continue;
 242         }
 243
 244         pa_atomic_sub(&f->data->in_pipe, (int) r);
 245     }
 246
 247     pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 248 }
 249
 250 int pa_fdsem_try(pa_fdsem *f) {
 251     pa_assert(f);
 252
 253     flush(f);
 254
 255     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 256         return 1;
 257
 258     return 0;
 259 }
 260
 261 int pa_fdsem_get(pa_fdsem *f) {
 262     pa_assert(f);
 263
 264 #ifdef HAVE_SYS_EVENTFD_H
 265     if (f->efd >= 0)
 266         return f->efd;
 267 #endif
 268
 269     return f->fds[0];
 270 }
 271
 272 int pa_fdsem_before_poll(pa_fdsem *f) {
 273     pa_assert(f);
 274
 275     flush(f);
 276
 277     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 278         return -1;
 279
 280     pa_atomic_inc(&f->data->waiting);
 281
 282     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
 283         pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 284         return -1;
 285     }
 286     return 0;
 287 }
 288
 289 int pa_fdsem_after_poll(pa_fdsem *f) {
 290     pa_assert(f);
 291
 292     pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 293
 294     flush(f);
 295
 296     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 297         return 1;
 298
 299     return 0;
 300 }