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 <pulsecore/core-error.h>
  39 #include <pulse/xmalloc.h>
  40
  41 #ifndef HAVE_PIPE
  42 #include <pulsecore/pipe.h>
  43 #endif
  44
  45 #ifdef HAVE_SYS_EVENTFD_H
  46 #include <sys/eventfd.h>
  47 #endif
  48
  49 #include "fdsem.h"
  50
  51 struct pa_fdsem {
  52     int fds[2];
  53 #ifdef HAVE_SYS_EVENTFD_H
  54     int efd;
  55 #endif
  56
  57     pa_fdsem_data *data;
  58 };
  59
  60 pa_fdsem *pa_fdsem_new(void) {
  61     pa_fdsem *f;
  62
  63     f = pa_xmalloc(PA_ALIGN(sizeof(pa_fdsem)) + PA_ALIGN(sizeof(pa_fdsem_data)));
  64
  65 #ifdef HAVE_SYS_EVENTFD_H
  66     if ((f->efd = eventfd(0, 0)) >= 0) {
  67         pa_make_fd_cloexec(f->efd);
  68         f->fds[0] = f->fds[1] = -1;
  69     } else
  70 #endif
  71     {
  72         if (pipe(f->fds) < 0) {
  73             pa_xfree(f);
  74             return NULL;
  75         }
  76
  77         pa_make_fd_cloexec(f->fds[0]);
  78         pa_make_fd_cloexec(f->fds[1]);
  79     }
  80
  81     f->data = (pa_fdsem_data*) ((uint8_t*) f + PA_ALIGN(sizeof(pa_fdsem)));
  82
  83     pa_atomic_store(&f->data->waiting, 0);
  84     pa_atomic_store(&f->data->signalled, 0);
  85     pa_atomic_store(&f->data->in_pipe, 0);
  86
  87     return f;
  88 }
  89
  90 pa_fdsem *pa_fdsem_open_shm(pa_fdsem_data *data, int event_fd) {
  91     pa_fdsem *f = NULL;
  92
  93     pa_assert(data);
  94     pa_assert(event_fd >= 0);
  95
  96 #ifdef HAVE_SYS_EVENTFD_H
  97     f = pa_xnew(pa_fdsem, 1);
  98
  99     f->efd = event_fd;
 100     pa_make_fd_cloexec(f->efd);
 101     f->fds[0] = f->fds[1] = -1;
 102     f->data = data;
 103 #endif
 104
 105     return f;
 106 }
 107
 108 pa_fdsem *pa_fdsem_new_shm(pa_fdsem_data *data, int* event_fd) {
 109     pa_fdsem *f = NULL;
 110
 111     pa_assert(data);
 112     pa_assert(event_fd);
 113
 114 #ifdef HAVE_SYS_EVENTFD_H
 115
 116     f = pa_xnew(pa_fdsem, 1);
 117
 118     if ((f->efd = eventfd(0, 0)) < 0) {
 119         pa_xfree(f);
 120         return NULL;
 121     }
 122
 123     pa_make_fd_cloexec(f->efd);
 124     f->fds[0] = f->fds[1] = -1;
 125     f->data = data;
 126
 127     pa_atomic_store(&f->data->waiting, 0);
 128     pa_atomic_store(&f->data->signalled, 0);
 129     pa_atomic_store(&f->data->in_pipe, 0);
 130
 131 #endif
 132
 133     return f;
 134 }
 135
 136 void pa_fdsem_free(pa_fdsem *f) {
 137     pa_assert(f);
 138
 139 #ifdef HAVE_SYS_EVENTFD_H
 140     if (f->efd >= 0)
 141         pa_close(f->efd);
 142 #endif
 143     pa_close_pipe(f->fds);
 144
 145     pa_xfree(f);
 146 }
 147
 148 static void flush(pa_fdsem *f) {
 149     ssize_t r;
 150     pa_assert(f);
 151
 152     if (pa_atomic_load(&f->data->in_pipe) <= 0)
 153         return;
 154
 155     do {
 156         char x[10];
 157
 158 #ifdef HAVE_SYS_EVENTFD_H
 159         if (f->efd >= 0) {
 160             uint64_t u;
 161
 162             if ((r = read(f->efd, &u, sizeof(u))) != sizeof(u)) {
 163
 164                 if (r >= 0 || errno != EINTR) {
 165                     pa_log_error("Invalid read from eventfd: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 166                     pa_assert_not_reached();
 167                 }
 168
 169                 continue;
 170             }
 171             r = (ssize_t) u;
 172         } else
 173 #endif
 174
 175         if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) {
 176
 177             if (r >= 0 || errno != EINTR) {
 178                 pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 179                 pa_assert_not_reached();
 180             }
 181
 182             continue;
 183         }
 184
 185     } while (pa_atomic_sub(&f->data->in_pipe, (int) r) > (int) r);
 186 }
 187
 188 void pa_fdsem_post(pa_fdsem *f) {
 189     pa_assert(f);
 190
 191     if (pa_atomic_cmpxchg(&f->data->signalled, 0, 1)) {
 192
 193         if (pa_atomic_load(&f->data->waiting)) {
 194             ssize_t r;
 195             char x = 'x';
 196
 197             pa_atomic_inc(&f->data->in_pipe);
 198
 199             for (;;) {
 200
 201 #ifdef HAVE_SYS_EVENTFD_H
 202                 if (f->efd >= 0) {
 203                     uint64_t u = 1;
 204
 205                     if ((r = write(f->efd, &u, sizeof(u))) != sizeof(u)) {
 206                         if (r >= 0 || errno != EINTR) {
 207                             pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 208                             pa_assert_not_reached();
 209                         }
 210
 211                         continue;
 212                     }
 213                 } else
 214 #endif
 215
 216                 if ((r = write(f->fds[1], &x, 1)) != 1) {
 217                     if (r >= 0 || errno != EINTR) {
 218                         pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 219                         pa_assert_not_reached();
 220                     }
 221
 222                     continue;
 223                 }
 224
 225                 break;
 226             }
 227         }
 228     }
 229 }
 230
 231 void pa_fdsem_wait(pa_fdsem *f) {
 232     pa_assert(f);
 233
 234     flush(f);
 235
 236     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 237         return;
 238
 239     pa_atomic_inc(&f->data->waiting);
 240
 241     while (!pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
 242         char x[10];
 243         ssize_t r;
 244
 245 #ifdef HAVE_SYS_EVENTFD_H
 246         if (f->efd >= 0) {
 247             uint64_t u;
 248
 249             if ((r = read(f->efd, &u, sizeof(u))) != sizeof(u)) {
 250
 251                 if (r >= 0 || errno != EINTR) {
 252                     pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 253                     pa_assert_not_reached();
 254                 }
 255
 256                 continue;
 257             }
 258
 259             r = (ssize_t) u;
 260         } else
 261 #endif
 262
 263         if ((r = read(f->fds[0], &x, sizeof(x))) <= 0) {
 264
 265             if (r >= 0 || errno != EINTR) {
 266                 pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 267                 pa_assert_not_reached();
 268             }
 269
 270             continue;
 271         }
 272
 273         pa_atomic_sub(&f->data->in_pipe, (int) r);
 274     }
 275
 276     pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 277 }
 278
 279 int pa_fdsem_try(pa_fdsem *f) {
 280     pa_assert(f);
 281
 282     flush(f);
 283
 284     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 285         return 1;
 286
 287     return 0;
 288 }
 289
 290 int pa_fdsem_get(pa_fdsem *f) {
 291     pa_assert(f);
 292
 293 #ifdef HAVE_SYS_EVENTFD_H
 294     if (f->efd >= 0)
 295         return f->efd;
 296 #endif
 297
 298     return f->fds[0];
 299 }
 300
 301 int pa_fdsem_before_poll(pa_fdsem *f) {
 302     pa_assert(f);
 303
 304     flush(f);
 305
 306     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 307         return -1;
 308
 309     pa_atomic_inc(&f->data->waiting);
 310
 311     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
 312         pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 313         return -1;
 314     }
 315     return 0;
 316 }
 317
 318 int pa_fdsem_after_poll(pa_fdsem *f) {
 319     pa_assert(f);
 320
 321     pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 322
 323     flush(f);
 324
 325     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 326         return 1;
 327
 328     return 0;
 329 }