code.delx.au - pulseaudio/blob - src/pulsecore/asyncq.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of PulseAudio.
   5
   6   Copyright 2006 Lennart Poettering
   7
   8   PulseAudio is free software; you can redistribute it and/or modify
   9   it under the terms of the GNU Lesser General Public License as
  10   published by the Free Software Foundation; either version 2.1 of the
  11   License, or (at your option) any later version.
  12
  13   PulseAudio is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public
  19   License along with PulseAudio; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  21   USA.
  22 ***/
  23
  24 #ifdef HAVE_CONFIG_H
  25 #include <config.h>
  26 #endif
  27
  28 #include <unistd.h>
  29 #include <errno.h>
  30
  31 #include <pulsecore/atomic.h>
  32 #include <pulsecore/log.h>
  33 #include <pulsecore/thread.h>
  34 #include <pulsecore/macro.h>
  35 #include <pulsecore/core-util.h>
  36 #include <pulse/xmalloc.h>
  37
  38 #include "asyncq.h"
  39
  40 #define ASYNCQ_SIZE 128
  41
  42 /* For debugging purposes we can define _Y to put and extra thread
  43  * yield between each operation. */
  44
  45 #ifdef PROFILE
  46 #define _Y pa_thread_yield()
  47 #else
  48 #define _Y do { } while(0)
  49 #endif
  50
  51 struct pa_asyncq {
  52     unsigned size;
  53     unsigned read_idx;
  54     unsigned write_idx;
  55     pa_atomic_int_t read_waiting;
  56     pa_atomic_int_t write_waiting;
  57     int read_fds[2], write_fds[2];
  58 };
  59
  60 #define PA_ASYNCQ_CELLS(x) ((pa_atomic_ptr_t*) ((uint8_t*) (x) + PA_ALIGN(sizeof(struct pa_asyncq))))
  61
  62 static int is_power_of_two(unsigned size) {
  63     return !(size & (size - 1));
  64 }
  65
  66 static int reduce(pa_asyncq *l, int value) {
  67     return value & (unsigned) (l->size - 1);
  68 }
  69
  70 pa_asyncq *pa_asyncq_new(unsigned size) {
  71     pa_asyncq *l;
  72
  73     if (!size)
  74         size = ASYNCQ_SIZE;
  75
  76     pa_assert(is_power_of_two(size));
  77
  78     l = pa_xmalloc0(PA_ALIGN(sizeof(pa_asyncq)) + (sizeof(pa_atomic_ptr_t) * size));
  79
  80     l->size = size;
  81     pa_atomic_store(&l->read_waiting, 0);
  82     pa_atomic_store(&l->write_waiting, 0);
  83
  84     if (pipe(l->read_fds) < 0) {
  85         pa_xfree(l);
  86         return NULL;
  87     }
  88
  89     if (pipe(l->write_fds) < 0) {
  90         pa_close(l->read_fds[0]);
  91         pa_close(l->read_fds[1]);
  92         pa_xfree(l);
  93         return NULL;
  94     }
  95
  96     pa_make_nonblock_fd(l->read_fds[1]);
  97     pa_make_nonblock_fd(l->write_fds[1]);
  98
  99     return l;
 100 }
 101
 102 void pa_asyncq_free(pa_asyncq *l, pa_free_cb_t free_cb) {
 103     pa_assert(l);
 104
 105     if (free_cb) {
 106         void *p;
 107
 108         while ((p = pa_asyncq_pop(l, 0)))
 109             free_cb(p);
 110     }
 111
 112     pa_close(l->read_fds[0]);
 113     pa_close(l->read_fds[1]);
 114     pa_close(l->write_fds[0]);
 115     pa_close(l->write_fds[1]);
 116
 117     pa_xfree(l);
 118 }
 119
 120 int pa_asyncq_push(pa_asyncq*l, void *p, int wait) {
 121     int idx;
 122     pa_atomic_ptr_t *cells;
 123
 124     pa_assert(l);
 125     pa_assert(p);
 126
 127     cells = PA_ASYNCQ_CELLS(l);
 128
 129     _Y;
 130     idx = reduce(l, l->write_idx);
 131
 132     if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) {
 133
 134         /* First try failed. Let's wait for changes. */
 135
 136         if (!wait)
 137             return -1;
 138
 139         _Y;
 140
 141         pa_atomic_inc(&l->write_waiting);
 142
 143         for (;;) {
 144             char x[20];
 145
 146             _Y;
 147
 148             if (pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p))
 149                 break;
 150
 151             _Y;
 152
 153             if (read(l->write_fds[0], x, sizeof(x)) < 0 && errno != EINTR) {
 154                 pa_atomic_dec(&l->write_waiting);
 155                 return -1;
 156             }
 157         }
 158
 159         _Y;
 160
 161         pa_atomic_dec(&l->write_waiting);
 162     }
 163
 164     _Y;
 165     l->write_idx++;
 166
 167     if (pa_atomic_load(&l->read_waiting)) {
 168         char x = 'x';
 169         _Y;
 170         write(l->read_fds[1], &x, sizeof(x));
 171     }
 172
 173     return 0;
 174 }
 175
 176 void* pa_asyncq_pop(pa_asyncq*l, int wait) {
 177     int idx;
 178     void *ret;
 179     pa_atomic_ptr_t *cells;
 180
 181     pa_assert(l);
 182
 183     cells = PA_ASYNCQ_CELLS(l);
 184
 185     _Y;
 186     idx = reduce(l, l->read_idx);
 187
 188     if (!(ret = pa_atomic_ptr_load(&cells[idx]))) {
 189
 190         /* First try failed. Let's wait for changes. */
 191
 192         if (!wait)
 193             return NULL;
 194
 195         _Y;
 196
 197         pa_atomic_inc(&l->read_waiting);
 198
 199         for (;;) {
 200             char x[20];
 201
 202             _Y;
 203
 204             if ((ret = pa_atomic_ptr_load(&cells[idx])))
 205                 break;
 206
 207             _Y;
 208
 209             if (read(l->read_fds[0], x, sizeof(x)) < 0 && errno != EINTR) {
 210                 pa_atomic_dec(&l->read_waiting);
 211                 return NULL;
 212             }
 213         }
 214
 215         _Y;
 216
 217         pa_atomic_dec(&l->read_waiting);
 218     }
 219
 220     /* Guaranteed if we only have a single reader */
 221     pa_assert_se(pa_atomic_ptr_cmpxchg(&cells[idx], ret, NULL));
 222
 223     _Y;
 224     l->read_idx++;
 225
 226     if (pa_atomic_load(&l->write_waiting)) {
 227         char x = 'x';
 228         _Y;
 229         write(l->write_fds[1], &x, sizeof(x));
 230     }
 231
 232     return ret;
 233 }
 234
 235 int pa_asyncq_get_fd(pa_asyncq *q) {
 236     pa_assert(q);
 237
 238     return q->read_fds[0];
 239 }
 240
 241 int pa_asyncq_before_poll(pa_asyncq *l) {
 242     int idx;
 243     pa_atomic_ptr_t *cells;
 244
 245     pa_assert(l);
 246
 247     cells = PA_ASYNCQ_CELLS(l);
 248
 249     _Y;
 250     idx = reduce(l, l->read_idx);
 251
 252     if (pa_atomic_ptr_load(&cells[idx]))
 253         return -1;
 254
 255     pa_atomic_inc(&l->read_waiting);
 256
 257     if (pa_atomic_ptr_load(&cells[idx])) {
 258         pa_atomic_dec(&l->read_waiting);
 259         return -1;
 260     }
 261
 262     return 0;
 263 }
 264
 265 int pa_asyncq_after_poll(pa_asyncq *l) {
 266     pa_assert(l);
 267
 268     pa_assert(pa_atomic_load(&l->read_waiting) > 0);
 269
 270     pa_atomic_dec(&l->read_waiting);
 271 }