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