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