code.delx.au - pulseaudio/blob - 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/macro.h>
  36 #include <pulsecore/core-util.h>
  37 #include <pulsecore/core-error.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     int write_type;
  56     pa_fdsem_data *data;
  57 };
  58
  59 pa_fdsem *pa_fdsem_new(void) {
  60     pa_fdsem *f;
  61
  62     f = pa_xmalloc0(PA_ALIGN(sizeof(pa_fdsem)) + PA_ALIGN(sizeof(pa_fdsem_data)));
  63
  64 #ifdef HAVE_SYS_EVENTFD_H
  65     if ((f->efd = eventfd(0, EFD_CLOEXEC)) >= 0)
  66         f->fds[0] = f->fds[1] = -1;
  67     else
  68 #endif
  69     {
  70         if (pa_pipe_cloexec(f->fds) < 0) {
  71             pa_xfree(f);
  72             return NULL;
  73         }
  74     }
  75
  76     f->data = (pa_fdsem_data*) ((uint8_t*) f + PA_ALIGN(sizeof(pa_fdsem)));
  77
  78     pa_atomic_store(&f->data->waiting, 0);
  79     pa_atomic_store(&f->data->signalled, 0);
  80     pa_atomic_store(&f->data->in_pipe, 0);
  81
  82     return f;
  83 }
  84
  85 pa_fdsem *pa_fdsem_open_shm(pa_fdsem_data *data, int event_fd) {
  86     pa_fdsem *f = NULL;
  87
  88     pa_assert(data);
  89     pa_assert(event_fd >= 0);
  90
  91 #ifdef HAVE_SYS_EVENTFD_H
  92     f = pa_xnew0(pa_fdsem, 1);
  93
  94     f->efd = event_fd;
  95     pa_make_fd_cloexec(f->efd);
  96     f->fds[0] = f->fds[1] = -1;
  97     f->data = data;
  98 #endif
  99
 100     return f;
 101 }
 102
 103 pa_fdsem *pa_fdsem_new_shm(pa_fdsem_data *data) {
 104     pa_fdsem *f = NULL;
 105
 106     pa_assert(data);
 107
 108 #ifdef HAVE_SYS_EVENTFD_H
 109
 110     f = pa_xnew0(pa_fdsem, 1);
 111
 112     if ((f->efd = eventfd(0, EFD_CLOEXEC)) < 0) {
 113         pa_xfree(f);
 114         return NULL;
 115     }
 116
 117     f->fds[0] = f->fds[1] = -1;
 118     f->data = data;
 119
 120     pa_atomic_store(&f->data->waiting, 0);
 121     pa_atomic_store(&f->data->signalled, 0);
 122     pa_atomic_store(&f->data->in_pipe, 0);
 123
 124 #endif
 125
 126     return f;
 127 }
 128
 129 void pa_fdsem_free(pa_fdsem *f) {
 130     pa_assert(f);
 131
 132 #ifdef HAVE_SYS_EVENTFD_H
 133     if (f->efd >= 0)
 134         pa_close(f->efd);
 135 #endif
 136     pa_close_pipe(f->fds);
 137
 138     pa_xfree(f);
 139 }
 140
 141 static void flush(pa_fdsem *f) {
 142     ssize_t r;
 143     pa_assert(f);
 144
 145     if (pa_atomic_load(&f->data->in_pipe) <= 0)
 146         return;
 147
 148     do {
 149         char x[10];
 150
 151 #ifdef HAVE_SYS_EVENTFD_H
 152         if (f->efd >= 0) {
 153             uint64_t u;
 154
 155             if ((r = pa_read(f->efd, &u, sizeof(u), NULL)) != sizeof(u)) {
 156
 157                 if (r >= 0 || errno != EINTR) {
 158                     pa_log_error("Invalid read from eventfd: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 159                     pa_assert_not_reached();
 160                 }
 161
 162                 continue;
 163             }
 164             r = (ssize_t) u;
 165         } else
 166 #endif
 167
 168         if ((r = pa_read(f->fds[0], &x, sizeof(x), NULL)) <= 0) {
 169
 170             if (r >= 0 || errno != EINTR) {
 171                 pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 172                 pa_assert_not_reached();
 173             }
 174
 175             continue;
 176         }
 177
 178     } while (pa_atomic_sub(&f->data->in_pipe, (int) r) > (int) r);
 179 }
 180
 181 void pa_fdsem_post(pa_fdsem *f) {
 182     pa_assert(f);
 183
 184     if (pa_atomic_cmpxchg(&f->data->signalled, 0, 1)) {
 185
 186         if (pa_atomic_load(&f->data->waiting)) {
 187             ssize_t r;
 188             char x = 'x';
 189
 190             pa_atomic_inc(&f->data->in_pipe);
 191
 192             for (;;) {
 193
 194 #ifdef HAVE_SYS_EVENTFD_H
 195                 if (f->efd >= 0) {
 196                     uint64_t u = 1;
 197
 198                     if ((r = pa_write(f->efd, &u, sizeof(u), &f->write_type)) != sizeof(u)) {
 199                         if (r >= 0 || errno != EINTR) {
 200                             pa_log_error("Invalid write to eventfd: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 201                             pa_assert_not_reached();
 202                         }
 203
 204                         continue;
 205                     }
 206                 } else
 207 #endif
 208
 209                 if ((r = pa_write(f->fds[1], &x, 1, &f->write_type)) != 1) {
 210                     if (r >= 0 || errno != EINTR) {
 211                         pa_log_error("Invalid write to pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 212                         pa_assert_not_reached();
 213                     }
 214
 215                     continue;
 216                 }
 217
 218                 break;
 219             }
 220         }
 221     }
 222 }
 223
 224 void pa_fdsem_wait(pa_fdsem *f) {
 225     pa_assert(f);
 226
 227     flush(f);
 228
 229     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 230         return;
 231
 232     pa_atomic_inc(&f->data->waiting);
 233
 234     while (!pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
 235         char x[10];
 236         ssize_t r;
 237
 238 #ifdef HAVE_SYS_EVENTFD_H
 239         if (f->efd >= 0) {
 240             uint64_t u;
 241
 242             if ((r = pa_read(f->efd, &u, sizeof(u), NULL)) != sizeof(u)) {
 243
 244                 if (r >= 0 || errno != EINTR) {
 245                     pa_log_error("Invalid read from eventfd: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 246                     pa_assert_not_reached();
 247                 }
 248
 249                 continue;
 250             }
 251
 252             r = (ssize_t) u;
 253         } else
 254 #endif
 255
 256         if ((r = pa_read(f->fds[0], &x, sizeof(x), NULL)) <= 0) {
 257
 258             if (r >= 0 || errno != EINTR) {
 259                 pa_log_error("Invalid read from pipe: %s", r < 0 ? pa_cstrerror(errno) : "EOF");
 260                 pa_assert_not_reached();
 261             }
 262
 263             continue;
 264         }
 265
 266         pa_atomic_sub(&f->data->in_pipe, (int) r);
 267     }
 268
 269     pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 270 }
 271
 272 int pa_fdsem_try(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     return 0;
 281 }
 282
 283 int pa_fdsem_get(pa_fdsem *f) {
 284     pa_assert(f);
 285
 286 #ifdef HAVE_SYS_EVENTFD_H
 287     if (f->efd >= 0)
 288         return f->efd;
 289 #endif
 290
 291     return f->fds[0];
 292 }
 293
 294 int pa_fdsem_before_poll(pa_fdsem *f) {
 295     pa_assert(f);
 296
 297     flush(f);
 298
 299     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 300         return -1;
 301
 302     pa_atomic_inc(&f->data->waiting);
 303
 304     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0)) {
 305         pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 306         return -1;
 307     }
 308     return 0;
 309 }
 310
 311 int pa_fdsem_after_poll(pa_fdsem *f) {
 312     pa_assert(f);
 313
 314     pa_assert_se(pa_atomic_dec(&f->data->waiting) >= 1);
 315
 316     flush(f);
 317
 318     if (pa_atomic_cmpxchg(&f->data->signalled, 1, 0))
 319         return 1;
 320
 321     return 0;
 322 }