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 "main-loop.h"
  30 #include "trace.h"
  31
  32 static QTAILQ_HEAD(, Coroutine) unlock_bh_queue =
  33     QTAILQ_HEAD_INITIALIZER(unlock_bh_queue);
  34 static QEMUBH* unlock_bh;
  35
  36 static void qemu_co_queue_next_bh(void *opaque)
  37 {
  38     Coroutine *next;
  39
  40     trace_qemu_co_queue_next_bh();
  41     while ((next = QTAILQ_FIRST(&unlock_bh_queue))) {
  42         QTAILQ_REMOVE(&unlock_bh_queue, next, co_queue_next);
  43         qemu_coroutine_enter(next, NULL);
  44     }
  45 }
  46
  47 void qemu_co_queue_init(CoQueue *queue)
  48 {
  49     QTAILQ_INIT(&queue->entries);
  50
  51     if (!unlock_bh) {
  52         unlock_bh = qemu_bh_new(qemu_co_queue_next_bh, NULL);
  53     }
  54 }
  55
  56 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
  57 {
  58     Coroutine *self = qemu_coroutine_self();
  59     QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
  60     qemu_coroutine_yield();
  61     assert(qemu_in_coroutine());
  62 }
  63
  64 bool qemu_co_queue_next(CoQueue *queue)
  65 {
  66     Coroutine *next;
  67
  68     next = QTAILQ_FIRST(&queue->entries);
  69     if (next) {
  70         QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
  71         QTAILQ_INSERT_TAIL(&unlock_bh_queue, next, co_queue_next);
  72         trace_qemu_co_queue_next(next);
  73         qemu_bh_schedule(unlock_bh);
  74     }
  75
  76     return (next != NULL);
  77 }
  78
  79 bool qemu_co_queue_empty(CoQueue *queue)
  80 {
  81     return (QTAILQ_FIRST(&queue->entries) == NULL);
  82 }
  83
  84 void qemu_co_mutex_init(CoMutex *mutex)
  85 {
  86     memset(mutex, 0, sizeof(*mutex));
  87     qemu_co_queue_init(&mutex->queue);
  88 }
  89
  90 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
  91 {
  92     Coroutine *self = qemu_coroutine_self();
  93
  94     trace_qemu_co_mutex_lock_entry(mutex, self);
  95
  96     while (mutex->locked) {
  97         qemu_co_queue_wait(&mutex->queue);
  98     }
  99
 100     mutex->locked = true;
 101
 102     trace_qemu_co_mutex_lock_return(mutex, self);
 103 }
 104
 105 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 106 {
 107     Coroutine *self = qemu_coroutine_self();
 108
 109     trace_qemu_co_mutex_unlock_entry(mutex, self);
 110
 111     assert(mutex->locked == true);
 112     assert(qemu_in_coroutine());
 113
 114     mutex->locked = false;
 115     qemu_co_queue_next(&mutex->queue);
 116
 117     trace_qemu_co_mutex_unlock_return(mutex, self);
 118 }
 119
 120 void qemu_co_rwlock_init(CoRwlock *lock)
 121 {
 122     memset(lock, 0, sizeof(*lock));
 123     qemu_co_queue_init(&lock->queue);
 124 }
 125
 126 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 127 {
 128     while (lock->writer) {
 129         qemu_co_queue_wait(&lock->queue);
 130     }
 131     lock->reader++;
 132 }
 133
 134 void qemu_co_rwlock_unlock(CoRwlock *lock)
 135 {
 136     assert(qemu_in_coroutine());
 137     if (lock->writer) {
 138         lock->writer = false;
 139         while (!qemu_co_queue_empty(&lock->queue)) {
 140             /*
 141              * Wakeup every body. This will include some
 142              * writers too.
 143              */
 144             qemu_co_queue_next(&lock->queue);
 145         }
 146     } else {
 147         lock->reader--;
 148         assert(lock->reader >= 0);
 149         /* Wakeup only one waiting writer */
 150         if (!lock->reader) {
 151             qemu_co_queue_next(&lock->queue);
 152         }
 153     }
 154 }
 155
 156 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 157 {
 158     while (lock->writer || lock->reader) {
 159         qemu_co_queue_wait(&lock->queue);
 160     }
 161     lock->writer = true;
 162 }