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