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 static QEMUBH* unlock_bh;
  34
  35 static void qemu_co_queue_next_bh(void *opaque)
  36 {
  37     Coroutine *next;
  38
  39     trace_qemu_co_queue_next_bh();
  40     while ((next = QTAILQ_FIRST(&unlock_bh_queue))) {
  41         QTAILQ_REMOVE(&unlock_bh_queue, next, co_queue_next);
  42         qemu_coroutine_enter(next, NULL);
  43     }
  44 }
  45
  46 void qemu_co_queue_init(CoQueue *queue)
  47 {
  48     QTAILQ_INIT(&queue->entries);
  49
  50     if (!unlock_bh) {
  51         unlock_bh = qemu_bh_new(qemu_co_queue_next_bh, NULL);
  52     }
  53 }
  54
  55 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
  56 {
  57     Coroutine *self = qemu_coroutine_self();
  58     QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
  59     qemu_coroutine_yield();
  60     assert(qemu_in_coroutine());
  61 }
  62
  63 bool qemu_co_queue_next(CoQueue *queue)
  64 {
  65     Coroutine *next;
  66
  67     next = QTAILQ_FIRST(&queue->entries);
  68     if (next) {
  69         QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
  70         QTAILQ_INSERT_TAIL(&unlock_bh_queue, next, co_queue_next);
  71         trace_qemu_co_queue_next(next);
  72         qemu_bh_schedule(unlock_bh);
  73     }
  74
  75     return (next != NULL);
  76 }
  77
  78 bool qemu_co_queue_empty(CoQueue *queue)
  79 {
  80     return (QTAILQ_FIRST(&queue->entries) == NULL);
  81 }
  82
  83 void qemu_co_mutex_init(CoMutex *mutex)
  84 {
  85     memset(mutex, 0, sizeof(*mutex));
  86     qemu_co_queue_init(&mutex->queue);
  87 }
  88
  89 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
  90 {
  91     Coroutine *self = qemu_coroutine_self();
  92
  93     trace_qemu_co_mutex_lock_entry(mutex, self);
  94
  95     while (mutex->locked) {
  96         qemu_co_queue_wait(&mutex->queue);
  97     }
  98
  99     mutex->locked = true;
 100
 101     trace_qemu_co_mutex_lock_return(mutex, self);
 102 }
 103
 104 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 105 {
 106     Coroutine *self = qemu_coroutine_self();
 107
 108     trace_qemu_co_mutex_unlock_entry(mutex, self);
 109
 110     assert(mutex->locked == true);
 111     assert(qemu_in_coroutine());
 112
 113     mutex->locked = false;
 114     qemu_co_queue_next(&mutex->queue);
 115
 116     trace_qemu_co_mutex_unlock_return(mutex, self);
 117 }
 118
 119 void qemu_co_rwlock_init(CoRwlock *lock)
 120 {
 121     memset(lock, 0, sizeof(*lock));
 122     qemu_co_queue_init(&lock->queue);
 123 }
 124
 125 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 126 {
 127     while (lock->writer) {
 128         qemu_co_queue_wait(&lock->queue);
 129     }
 130     lock->reader++;
 131 }
 132
 133 void qemu_co_rwlock_unlock(CoRwlock *lock)
 134 {
 135     assert(qemu_in_coroutine());
 136     if (lock->writer) {
 137         lock->writer = false;
 138         while (!qemu_co_queue_empty(&lock->queue)) {
 139             /*
 140              * Wakeup every body. This will include some
 141              * writers too.
 142              */
 143             qemu_co_queue_next(&lock->queue);
 144         }
 145     } else {
 146         lock->reader--;
 147         assert(lock->reader >= 0);
 148         /* Wakeup only one waiting writer */
 149         if (!lock->reader) {
 150             qemu_co_queue_next(&lock->queue);
 151         }
 152     }
 153 }
 154
 155 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 156 {
 157     while (lock->writer || lock->reader) {
 158         qemu_co_queue_wait(&lock->queue);
 159     }
 160     lock->writer = true;
 161 }