qemu-coroutine-lock.c

   1 /*
   2  * coroutine queues and locks
   3  *
   4  * Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 #include "qemu-common.h"
  26 #include "qemu-coroutine.h"
  27 #include "qemu-coroutine-int.h"
  28 #include "qemu-queue.h"
  29 #include "trace.h"
  30
  31 static QTAILQ_HEAD(, Coroutine) unlock_bh_queue =
  32     QTAILQ_HEAD_INITIALIZER(unlock_bh_queue);
  33
  34 struct unlock_bh {
  35     QEMUBH *bh;
  36 };
  37
  38 static void qemu_co_queue_next_bh(void *opaque)
  39 {
  40     struct unlock_bh *unlock_bh = opaque;
  41     Coroutine *next;
  42
  43     trace_qemu_co_queue_next_bh();
  44     while ((next = QTAILQ_FIRST(&unlock_bh_queue))) {
  45         QTAILQ_REMOVE(&unlock_bh_queue, next, co_queue_next);
  46         qemu_coroutine_enter(next, NULL);
  47     }
  48
  49     qemu_bh_delete(unlock_bh->bh);
  50     qemu_free(unlock_bh);
  51 }
  52
  53 void qemu_co_queue_init(CoQueue *queue)
  54 {
  55     QTAILQ_INIT(&queue->entries);
  56 }
  57
  58 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
  59 {
  60     Coroutine *self = qemu_coroutine_self();
  61     QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
  62     qemu_coroutine_yield();
  63     assert(qemu_in_coroutine());
  64 }
  65
  66 bool qemu_co_queue_next(CoQueue *queue)
  67 {
  68     struct unlock_bh *unlock_bh;
  69     Coroutine *next;
  70
  71     next = QTAILQ_FIRST(&queue->entries);
  72     if (next) {
  73         QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
  74         QTAILQ_INSERT_TAIL(&unlock_bh_queue, next, co_queue_next);
  75         trace_qemu_co_queue_next(next);
  76
  77         unlock_bh = qemu_malloc(sizeof(*unlock_bh));
  78         unlock_bh->bh = qemu_bh_new(qemu_co_queue_next_bh, unlock_bh);
  79         qemu_bh_schedule(unlock_bh->bh);
  80     }
  81
  82     return (next != NULL);
  83 }
  84
  85 bool qemu_co_queue_empty(CoQueue *queue)
  86 {
  87     return (QTAILQ_FIRST(&queue->entries) == NULL);
  88 }
  89
  90 void qemu_co_mutex_init(CoMutex *mutex)
  91 {
  92     memset(mutex, 0, sizeof(*mutex));
  93     qemu_co_queue_init(&mutex->queue);
  94 }
  95
  96 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
  97 {
  98     Coroutine *self = qemu_coroutine_self();
  99
 100     trace_qemu_co_mutex_lock_entry(mutex, self);
 101
 102     while (mutex->locked) {
 103         qemu_co_queue_wait(&mutex->queue);
 104     }
 105
 106     mutex->locked = true;
 107
 108     trace_qemu_co_mutex_lock_return(mutex, self);
 109 }
 110
 111 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 112 {
 113     Coroutine *self = qemu_coroutine_self();
 114
 115     trace_qemu_co_mutex_unlock_entry(mutex, self);
 116
 117     assert(mutex->locked == true);
 118     assert(qemu_in_coroutine());
 119
 120     mutex->locked = false;
 121     qemu_co_queue_next(&mutex->queue);
 122
 123     trace_qemu_co_mutex_unlock_return(mutex, self);
 124 }