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 "block/coroutine.h"
  27 #include "block/coroutine_int.h"
  28 #include "qemu/queue.h"
  29 #include "block/aio.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 void coroutine_fn qemu_co_queue_wait_insert_head(CoQueue *queue)
  65 {
  66     Coroutine *self = qemu_coroutine_self();
  67     QTAILQ_INSERT_HEAD(&queue->entries, self, co_queue_next);
  68     qemu_coroutine_yield();
  69     assert(qemu_in_coroutine());
  70 }
  71
  72 bool qemu_co_queue_next(CoQueue *queue)
  73 {
  74     Coroutine *next;
  75
  76     next = QTAILQ_FIRST(&queue->entries);
  77     if (next) {
  78         QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
  79         QTAILQ_INSERT_TAIL(&unlock_bh_queue, next, co_queue_next);
  80         trace_qemu_co_queue_next(next);
  81         qemu_bh_schedule(unlock_bh);
  82     }
  83
  84     return (next != NULL);
  85 }
  86
  87 void qemu_co_queue_restart_all(CoQueue *queue)
  88 {
  89     while (qemu_co_queue_next(queue)) {
  90         /* Do nothing */
  91     }
  92 }
  93
  94 bool qemu_co_queue_empty(CoQueue *queue)
  95 {
  96     return (QTAILQ_FIRST(&queue->entries) == NULL);
  97 }
  98
  99 void qemu_co_mutex_init(CoMutex *mutex)
 100 {
 101     memset(mutex, 0, sizeof(*mutex));
 102     qemu_co_queue_init(&mutex->queue);
 103 }
 104
 105 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
 106 {
 107     Coroutine *self = qemu_coroutine_self();
 108
 109     trace_qemu_co_mutex_lock_entry(mutex, self);
 110
 111     while (mutex->locked) {
 112         qemu_co_queue_wait(&mutex->queue);
 113     }
 114
 115     mutex->locked = true;
 116
 117     trace_qemu_co_mutex_lock_return(mutex, self);
 118 }
 119
 120 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 121 {
 122     Coroutine *self = qemu_coroutine_self();
 123
 124     trace_qemu_co_mutex_unlock_entry(mutex, self);
 125
 126     assert(mutex->locked == true);
 127     assert(qemu_in_coroutine());
 128
 129     mutex->locked = false;
 130     qemu_co_queue_next(&mutex->queue);
 131
 132     trace_qemu_co_mutex_unlock_return(mutex, self);
 133 }
 134
 135 void qemu_co_rwlock_init(CoRwlock *lock)
 136 {
 137     memset(lock, 0, sizeof(*lock));
 138     qemu_co_queue_init(&lock->queue);
 139 }
 140
 141 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 142 {
 143     while (lock->writer) {
 144         qemu_co_queue_wait(&lock->queue);
 145     }
 146     lock->reader++;
 147 }
 148
 149 void qemu_co_rwlock_unlock(CoRwlock *lock)
 150 {
 151     assert(qemu_in_coroutine());
 152     if (lock->writer) {
 153         lock->writer = false;
 154         qemu_co_queue_restart_all(&lock->queue);
 155     } else {
 156         lock->reader--;
 157         assert(lock->reader >= 0);
 158         /* Wakeup only one waiting writer */
 159         if (!lock->reader) {
 160             qemu_co_queue_next(&lock->queue);
 161         }
 162     }
 163 }
 164
 165 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 166 {
 167     while (lock->writer || lock->reader) {
 168         qemu_co_queue_wait(&lock->queue);
 169     }
 170     lock->writer = true;
 171 }