src/pulsecore/asyncq.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2006-2008 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 #include <unistd.h>
  27 #include <errno.h>
  28
  29 #include <pulse/xmalloc.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 <pulsecore/llist.h>
  37 #include <pulsecore/flist.h>
  38 #include <pulsecore/fdsem.h>
  39
  40 #include "asyncq.h"
  41
  42 #define ASYNCQ_SIZE 256
  43
  44 /* For debugging purposes we can define _Y to put an extra thread
  45  * yield between each operation. */
  46
  47 /* #define PROFILE */
  48
  49 #ifdef PROFILE
  50 #define _Y pa_thread_yield()
  51 #else
  52 #define _Y do { } while(0)
  53 #endif
  54
  55 struct localq {
  56     void *data;
  57     PA_LLIST_FIELDS(struct localq);
  58 };
  59
  60 struct pa_asyncq {
  61     unsigned size;
  62     unsigned read_idx;
  63     unsigned write_idx;
  64     pa_fdsem *read_fdsem, *write_fdsem;
  65
  66     PA_LLIST_HEAD(struct localq, localq);
  67     struct localq *last_localq;
  68     pa_bool_t waiting_for_post;
  69 };
  70
  71 PA_STATIC_FLIST_DECLARE(localq, 0, pa_xfree);
  72
  73 #define PA_ASYNCQ_CELLS(x) ((pa_atomic_ptr_t*) ((uint8_t*) (x) + PA_ALIGN(sizeof(struct pa_asyncq))))
  74
  75 static unsigned reduce(pa_asyncq *l, unsigned value) {
  76     return value & (unsigned) (l->size - 1);
  77 }
  78
  79 pa_asyncq *pa_asyncq_new(unsigned size) {
  80     pa_asyncq *l;
  81
  82     if (!size)
  83         size = ASYNCQ_SIZE;
  84
  85     pa_assert(pa_is_power_of_two(size));
  86
  87     l = pa_xmalloc0(PA_ALIGN(sizeof(pa_asyncq)) + (sizeof(pa_atomic_ptr_t) * size));
  88
  89     l->size = size;
  90
  91     PA_LLIST_HEAD_INIT(struct localq, l->localq);
  92     l->last_localq = NULL;
  93     l->waiting_for_post = FALSE;
  94
  95     if (!(l->read_fdsem = pa_fdsem_new())) {
  96         pa_xfree(l);
  97         return NULL;
  98     }
  99
 100     if (!(l->write_fdsem = pa_fdsem_new())) {
 101         pa_fdsem_free(l->read_fdsem);
 102         pa_xfree(l);
 103         return NULL;
 104     }
 105
 106     return l;
 107 }
 108
 109 void pa_asyncq_free(pa_asyncq *l, pa_free_cb_t free_cb) {
 110     struct localq *q;
 111     pa_assert(l);
 112
 113     if (free_cb) {
 114         void *p;
 115
 116         while ((p = pa_asyncq_pop(l, 0)))
 117             free_cb(p);
 118     }
 119
 120     while ((q = l->localq)) {
 121         if (free_cb)
 122             free_cb(q->data);
 123
 124         PA_LLIST_REMOVE(struct localq, l->localq, q);
 125
 126         if (pa_flist_push(PA_STATIC_FLIST_GET(localq), q) < 0)
 127             pa_xfree(q);
 128     }
 129
 130     pa_fdsem_free(l->read_fdsem);
 131     pa_fdsem_free(l->write_fdsem);
 132     pa_xfree(l);
 133 }
 134
 135 static int push(pa_asyncq*l, void *p, pa_bool_t wait_op) {
 136     unsigned idx;
 137     pa_atomic_ptr_t *cells;
 138
 139     pa_assert(l);
 140     pa_assert(p);
 141
 142     cells = PA_ASYNCQ_CELLS(l);
 143
 144     _Y;
 145     idx = reduce(l, l->write_idx);
 146
 147     if (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p)) {
 148
 149         if (!wait_op)
 150             return -1;
 151
 152 /*         pa_log("sleeping on push"); */
 153
 154         do {
 155             pa_fdsem_wait(l->read_fdsem);
 156         } while (!pa_atomic_ptr_cmpxchg(&cells[idx], NULL, p));
 157     }
 158
 159     _Y;
 160     l->write_idx++;
 161
 162     pa_fdsem_post(l->write_fdsem);
 163
 164     return 0;
 165 }
 166
 167 static pa_bool_t flush_postq(pa_asyncq *l, pa_bool_t wait_op) {
 168     struct localq *q;
 169
 170     pa_assert(l);
 171
 172     while ((q = l->last_localq)) {
 173
 174         if (push(l, q->data, wait_op) < 0)
 175             return FALSE;
 176
 177         l->last_localq = q->prev;
 178
 179         PA_LLIST_REMOVE(struct localq, l->localq, q);
 180
 181         if (pa_flist_push(PA_STATIC_FLIST_GET(localq), q) < 0)
 182             pa_xfree(q);
 183     }
 184
 185     return TRUE;
 186 }
 187
 188 int pa_asyncq_push(pa_asyncq*l, void *p, pa_bool_t wait_op) {
 189     pa_assert(l);
 190
 191     if (!flush_postq(l, wait_op))
 192         return -1;
 193
 194     return push(l, p, wait_op);
 195 }
 196
 197 void pa_asyncq_post(pa_asyncq*l, void *p) {
 198     struct localq *q;
 199
 200     pa_assert(l);
 201     pa_assert(p);
 202
 203     if (flush_postq(l, FALSE))
 204         if (pa_asyncq_push(l, p, FALSE) >= 0)
 205             return;
 206
 207     /* OK, we couldn't push anything in the queue. So let's queue it
 208      * locally and push it later */
 209
 210     if (pa_log_ratelimit(PA_LOG_WARN))
 211         pa_log_warn("q overrun, queuing locally");
 212
 213     if (!(q = pa_flist_pop(PA_STATIC_FLIST_GET(localq))))
 214         q = pa_xnew(struct localq, 1);
 215
 216     q->data = p;
 217     PA_LLIST_PREPEND(struct localq, l->localq, q);
 218
 219     if (!l->last_localq)
 220         l->last_localq = q;
 221
 222     return;
 223 }
 224
 225 void* pa_asyncq_pop(pa_asyncq*l, pa_bool_t wait_op) {
 226     unsigned idx;
 227     void *ret;
 228     pa_atomic_ptr_t *cells;
 229
 230     pa_assert(l);
 231
 232     cells = PA_ASYNCQ_CELLS(l);
 233
 234     _Y;
 235     idx = reduce(l, l->read_idx);
 236
 237     if (!(ret = pa_atomic_ptr_load(&cells[idx]))) {
 238
 239         if (!wait_op)
 240             return NULL;
 241
 242 /*         pa_log("sleeping on pop"); */
 243
 244         do {
 245             pa_fdsem_wait(l->write_fdsem);
 246         } while (!(ret = pa_atomic_ptr_load(&cells[idx])));
 247     }
 248
 249     pa_assert(ret);
 250
 251     /* Guaranteed to succeed if we only have a single reader */
 252     pa_assert_se(pa_atomic_ptr_cmpxchg(&cells[idx], ret, NULL));
 253
 254     _Y;
 255     l->read_idx++;
 256
 257     pa_fdsem_post(l->read_fdsem);
 258
 259     return ret;
 260 }
 261
 262 int pa_asyncq_read_fd(pa_asyncq *q) {
 263     pa_assert(q);
 264
 265     return pa_fdsem_get(q->write_fdsem);
 266 }
 267
 268 int pa_asyncq_read_before_poll(pa_asyncq *l) {
 269     unsigned idx;
 270     pa_atomic_ptr_t *cells;
 271
 272     pa_assert(l);
 273
 274     cells = PA_ASYNCQ_CELLS(l);
 275
 276     _Y;
 277     idx = reduce(l, l->read_idx);
 278
 279     for (;;) {
 280         if (pa_atomic_ptr_load(&cells[idx]))
 281             return -1;
 282
 283         if (pa_fdsem_before_poll(l->write_fdsem) >= 0)
 284             return 0;
 285     }
 286 }
 287
 288 void pa_asyncq_read_after_poll(pa_asyncq *l) {
 289     pa_assert(l);
 290
 291     pa_fdsem_after_poll(l->write_fdsem);
 292 }
 293
 294 int pa_asyncq_write_fd(pa_asyncq *q) {
 295     pa_assert(q);
 296
 297     return pa_fdsem_get(q->read_fdsem);
 298 }
 299
 300 void pa_asyncq_write_before_poll(pa_asyncq *l) {
 301     pa_assert(l);
 302
 303     for (;;) {
 304
 305         if (flush_postq(l, FALSE))
 306             break;
 307
 308         if (pa_fdsem_before_poll(l->read_fdsem) >= 0) {
 309             l->waiting_for_post = TRUE;
 310             break;
 311         }
 312     }
 313 }
 314
 315 void pa_asyncq_write_after_poll(pa_asyncq *l) {
 316     pa_assert(l);
 317
 318     if (l->waiting_for_post) {
 319         pa_fdsem_after_poll(l->read_fdsem);
 320         l->waiting_for_post = FALSE;
 321     }
 322 }