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/osdep.h"
  26 #include "qemu-common.h"
  27 #include "qemu/coroutine.h"
  28 #include "qemu/coroutine_int.h"
  29 #include "qemu/queue.h"
  30 #include "block/aio.h"
  31 #include "trace.h"
  32
  33 void qemu_co_queue_init(CoQueue *queue)
  34 {
  35     QSIMPLEQ_INIT(&queue->entries);
  36 }
  37
  38 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
  39 {
  40     Coroutine *self = qemu_coroutine_self();
  41     QSIMPLEQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
  42     qemu_coroutine_yield();
  43     assert(qemu_in_coroutine());
  44 }
  45
  46 /**
  47  * qemu_co_queue_run_restart:
  48  *
  49  * Enter each coroutine that was previously marked for restart by
  50  * qemu_co_queue_next() or qemu_co_queue_restart_all().  This function is
  51  * invoked by the core coroutine code when the current coroutine yields or
  52  * terminates.
  53  */
  54 void qemu_co_queue_run_restart(Coroutine *co)
  55 {
  56     Coroutine *next;
  57
  58     trace_qemu_co_queue_run_restart(co);
  59     while ((next = QSIMPLEQ_FIRST(&co->co_queue_wakeup))) {
  60         QSIMPLEQ_REMOVE_HEAD(&co->co_queue_wakeup, co_queue_next);
  61         qemu_coroutine_enter(next);
  62     }
  63 }
  64
  65 static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
  66 {
  67     Coroutine *next;
  68
  69     if (QSIMPLEQ_EMPTY(&queue->entries)) {
  70         return false;
  71     }
  72
  73     while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) {
  74         QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
  75         aio_co_wake(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 = QSIMPLEQ_FIRST(&queue->entries);
 100     if (!next) {
 101         return false;
 102     }
 103
 104     QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
 105     qemu_coroutine_enter(next);
 106     return true;
 107 }
 108
 109 bool qemu_co_queue_empty(CoQueue *queue)
 110 {
 111     return QSIMPLEQ_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     mutex->holder = self;
 132     self->locks_held++;
 133
 134     trace_qemu_co_mutex_lock_return(mutex, self);
 135 }
 136
 137 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 138 {
 139     Coroutine *self = qemu_coroutine_self();
 140
 141     trace_qemu_co_mutex_unlock_entry(mutex, self);
 142
 143     assert(mutex->locked == true);
 144     assert(mutex->holder == self);
 145     assert(qemu_in_coroutine());
 146
 147     mutex->locked = false;
 148     mutex->holder = NULL;
 149     self->locks_held--;
 150     qemu_co_queue_next(&mutex->queue);
 151
 152     trace_qemu_co_mutex_unlock_return(mutex, self);
 153 }
 154
 155 void qemu_co_rwlock_init(CoRwlock *lock)
 156 {
 157     memset(lock, 0, sizeof(*lock));
 158     qemu_co_queue_init(&lock->queue);
 159 }
 160
 161 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 162 {
 163     Coroutine *self = qemu_coroutine_self();
 164
 165     while (lock->writer) {
 166         qemu_co_queue_wait(&lock->queue);
 167     }
 168     lock->reader++;
 169     self->locks_held++;
 170 }
 171
 172 void qemu_co_rwlock_unlock(CoRwlock *lock)
 173 {
 174     Coroutine *self = qemu_coroutine_self();
 175
 176     assert(qemu_in_coroutine());
 177     if (lock->writer) {
 178         lock->writer = false;
 179         qemu_co_queue_restart_all(&lock->queue);
 180     } else {
 181         lock->reader--;
 182         assert(lock->reader >= 0);
 183         /* Wakeup only one waiting writer */
 184         if (!lock->reader) {
 185             qemu_co_queue_next(&lock->queue);
 186         }
 187     }
 188     self->locks_held--;
 189 }
 190
 191 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 192 {
 193     Coroutine *self = qemu_coroutine_self();
 194
 195     while (lock->writer || lock->reader) {
 196         qemu_co_queue_wait(&lock->queue);
 197     }
 198     lock->writer = true;
 199     self->locks_held++;
 200 }