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 "trace.h"
  30
  31 void qemu_co_queue_init(CoQueue *queue)
  32 {
  33     QTAILQ_INIT(&queue->entries);
  34 }
  35
  36 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
  37 {
  38     Coroutine *self = qemu_coroutine_self();
  39     QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
  40     qemu_coroutine_yield();
  41     assert(qemu_in_coroutine());
  42 }
  43
  44 void coroutine_fn qemu_co_queue_wait_insert_head(CoQueue *queue)
  45 {
  46     Coroutine *self = qemu_coroutine_self();
  47     QTAILQ_INSERT_HEAD(&queue->entries, self, co_queue_next);
  48     qemu_coroutine_yield();
  49     assert(qemu_in_coroutine());
  50 }
  51
  52 /**
  53  * qemu_co_queue_run_restart:
  54  *
  55  * Enter each coroutine that was previously marked for restart by
  56  * qemu_co_queue_next() or qemu_co_queue_restart_all().  This function is
  57  * invoked by the core coroutine code when the current coroutine yields or
  58  * terminates.
  59  */
  60 void qemu_co_queue_run_restart(Coroutine *co)
  61 {
  62     Coroutine *next;
  63
  64     trace_qemu_co_queue_run_restart(co);
  65     while ((next = QTAILQ_FIRST(&co->co_queue_wakeup))) {
  66         QTAILQ_REMOVE(&co->co_queue_wakeup, next, co_queue_next);
  67         qemu_coroutine_enter(next, NULL);
  68     }
  69 }
  70
  71 static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
  72 {
  73     Coroutine *self = qemu_coroutine_self();
  74     Coroutine *next;
  75
  76     if (QTAILQ_EMPTY(&queue->entries)) {
  77         return false;
  78     }
  79
  80     while ((next = QTAILQ_FIRST(&queue->entries)) != NULL) {
  81         QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
  82         QTAILQ_INSERT_TAIL(&self->co_queue_wakeup, next, co_queue_next);
  83         trace_qemu_co_queue_next(next);
  84         if (single) {
  85             break;
  86         }
  87     }
  88     return true;
  89 }
  90
  91 bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
  92 {
  93     assert(qemu_in_coroutine());
  94     return qemu_co_queue_do_restart(queue, true);
  95 }
  96
  97 void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue)
  98 {
  99     assert(qemu_in_coroutine());
 100     qemu_co_queue_do_restart(queue, false);
 101 }
 102
 103 bool qemu_co_enter_next(CoQueue *queue)
 104 {
 105     Coroutine *next;
 106
 107     next = QTAILQ_FIRST(&queue->entries);
 108     if (!next) {
 109         return false;
 110     }
 111
 112     QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
 113     qemu_coroutine_enter(next, NULL);
 114     return true;
 115 }
 116
 117 bool qemu_co_queue_empty(CoQueue *queue)
 118 {
 119     return (QTAILQ_FIRST(&queue->entries) == NULL);
 120 }
 121
 122 void qemu_co_mutex_init(CoMutex *mutex)
 123 {
 124     memset(mutex, 0, sizeof(*mutex));
 125     qemu_co_queue_init(&mutex->queue);
 126 }
 127
 128 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
 129 {
 130     Coroutine *self = qemu_coroutine_self();
 131
 132     trace_qemu_co_mutex_lock_entry(mutex, self);
 133
 134     while (mutex->locked) {
 135         qemu_co_queue_wait(&mutex->queue);
 136     }
 137
 138     mutex->locked = true;
 139
 140     trace_qemu_co_mutex_lock_return(mutex, self);
 141 }
 142
 143 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 144 {
 145     Coroutine *self = qemu_coroutine_self();
 146
 147     trace_qemu_co_mutex_unlock_entry(mutex, self);
 148
 149     assert(mutex->locked == true);
 150     assert(qemu_in_coroutine());
 151
 152     mutex->locked = false;
 153     qemu_co_queue_next(&mutex->queue);
 154
 155     trace_qemu_co_mutex_unlock_return(mutex, self);
 156 }
 157
 158 void qemu_co_rwlock_init(CoRwlock *lock)
 159 {
 160     memset(lock, 0, sizeof(*lock));
 161     qemu_co_queue_init(&lock->queue);
 162 }
 163
 164 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 165 {
 166     while (lock->writer) {
 167         qemu_co_queue_wait(&lock->queue);
 168     }
 169     lock->reader++;
 170 }
 171
 172 void qemu_co_rwlock_unlock(CoRwlock *lock)
 173 {
 174     assert(qemu_in_coroutine());
 175     if (lock->writer) {
 176         lock->writer = false;
 177         qemu_co_queue_restart_all(&lock->queue);
 178     } else {
 179         lock->reader--;
 180         assert(lock->reader >= 0);
 181         /* Wakeup only one waiting writer */
 182         if (!lock->reader) {
 183             qemu_co_queue_next(&lock->queue);
 184         }
 185     }
 186 }
 187
 188 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 189 {
 190     while (lock->writer || lock->reader) {
 191         qemu_co_queue_wait(&lock->queue);
 192     }
 193     lock->writer = true;
 194 }