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