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 "trace.h"
  31
  32 void qemu_co_queue_init(CoQueue *queue)
  33 {
  34     QSIMPLEQ_INIT(&queue->entries);
  35 }
  36
  37 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
  38 {
  39     Coroutine *self = qemu_coroutine_self();
  40     QSIMPLEQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
  41     qemu_coroutine_yield();
  42     assert(qemu_in_coroutine());
  43 }
  44
  45 /**
  46  * qemu_co_queue_run_restart:
  47  *
  48  * Enter each coroutine that was previously marked for restart by
  49  * qemu_co_queue_next() or qemu_co_queue_restart_all().  This function is
  50  * invoked by the core coroutine code when the current coroutine yields or
  51  * terminates.
  52  */
  53 void qemu_co_queue_run_restart(Coroutine *co)
  54 {
  55     Coroutine *next;
  56
  57     trace_qemu_co_queue_run_restart(co);
  58     while ((next = QSIMPLEQ_FIRST(&co->co_queue_wakeup))) {
  59         QSIMPLEQ_REMOVE_HEAD(&co->co_queue_wakeup, co_queue_next);
  60         qemu_coroutine_enter(next);
  61     }
  62 }
  63
  64 static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
  65 {
  66     Coroutine *self = qemu_coroutine_self();
  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         QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, next, co_queue_next);
  76         trace_qemu_co_queue_next(next);
  77         if (single) {
  78             break;
  79         }
  80     }
  81     return true;
  82 }
  83
  84 bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
  85 {
  86     assert(qemu_in_coroutine());
  87     return qemu_co_queue_do_restart(queue, true);
  88 }
  89
  90 void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue)
  91 {
  92     assert(qemu_in_coroutine());
  93     qemu_co_queue_do_restart(queue, false);
  94 }
  95
  96 bool qemu_co_enter_next(CoQueue *queue)
  97 {
  98     Coroutine *next;
  99
 100     next = QSIMPLEQ_FIRST(&queue->entries);
 101     if (!next) {
 102         return false;
 103     }
 104
 105     QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
 106     qemu_coroutine_enter(next);
 107     return true;
 108 }
 109
 110 bool qemu_co_queue_empty(CoQueue *queue)
 111 {
 112     return QSIMPLEQ_FIRST(&queue->entries) == NULL;
 113 }
 114
 115 void qemu_co_mutex_init(CoMutex *mutex)
 116 {
 117     memset(mutex, 0, sizeof(*mutex));
 118     qemu_co_queue_init(&mutex->queue);
 119 }
 120
 121 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
 122 {
 123     Coroutine *self = qemu_coroutine_self();
 124
 125     trace_qemu_co_mutex_lock_entry(mutex, self);
 126
 127     while (mutex->locked) {
 128         qemu_co_queue_wait(&mutex->queue);
 129     }
 130
 131     mutex->locked = true;
 132     mutex->holder = self;
 133     self->locks_held++;
 134
 135     trace_qemu_co_mutex_lock_return(mutex, self);
 136 }
 137
 138 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 139 {
 140     Coroutine *self = qemu_coroutine_self();
 141
 142     trace_qemu_co_mutex_unlock_entry(mutex, self);
 143
 144     assert(mutex->locked == true);
 145     assert(mutex->holder == self);
 146     assert(qemu_in_coroutine());
 147
 148     mutex->locked = false;
 149     mutex->holder = NULL;
 150     self->locks_held--;
 151     qemu_co_queue_next(&mutex->queue);
 152
 153     trace_qemu_co_mutex_unlock_return(mutex, self);
 154 }
 155
 156 void qemu_co_rwlock_init(CoRwlock *lock)
 157 {
 158     memset(lock, 0, sizeof(*lock));
 159     qemu_co_queue_init(&lock->queue);
 160 }
 161
 162 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 163 {
 164     Coroutine *self = qemu_coroutine_self();
 165
 166     while (lock->writer) {
 167         qemu_co_queue_wait(&lock->queue);
 168     }
 169     lock->reader++;
 170     self->locks_held++;
 171 }
 172
 173 void qemu_co_rwlock_unlock(CoRwlock *lock)
 174 {
 175     Coroutine *self = qemu_coroutine_self();
 176
 177     assert(qemu_in_coroutine());
 178     if (lock->writer) {
 179         lock->writer = false;
 180         qemu_co_queue_restart_all(&lock->queue);
 181     } else {
 182         lock->reader--;
 183         assert(lock->reader >= 0);
 184         /* Wakeup only one waiting writer */
 185         if (!lock->reader) {
 186             qemu_co_queue_next(&lock->queue);
 187         }
 188     }
 189     self->locks_held--;
 190 }
 191
 192 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 193 {
 194     Coroutine *self = qemu_coroutine_self();
 195
 196     while (lock->writer || lock->reader) {
 197         qemu_co_queue_wait(&lock->queue);
 198     }
 199     lock->writer = true;
 200     self->locks_held++;
 201 }