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 qemu_co_queue_next(CoQueue *queue)
  92 {
  93     return qemu_co_queue_do_restart(queue, true);
  94 }
  95
  96 void qemu_co_queue_restart_all(CoQueue *queue)
  97 {
  98     qemu_co_queue_do_restart(queue, false);
  99 }
 100
 101 bool qemu_co_queue_empty(CoQueue *queue)
 102 {
 103     return (QTAILQ_FIRST(&queue->entries) == NULL);
 104 }
 105
 106 void qemu_co_mutex_init(CoMutex *mutex)
 107 {
 108     memset(mutex, 0, sizeof(*mutex));
 109     qemu_co_queue_init(&mutex->queue);
 110 }
 111
 112 void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
 113 {
 114     Coroutine *self = qemu_coroutine_self();
 115
 116     trace_qemu_co_mutex_lock_entry(mutex, self);
 117
 118     while (mutex->locked) {
 119         qemu_co_queue_wait(&mutex->queue);
 120     }
 121
 122     mutex->locked = true;
 123
 124     trace_qemu_co_mutex_lock_return(mutex, self);
 125 }
 126
 127 void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
 128 {
 129     Coroutine *self = qemu_coroutine_self();
 130
 131     trace_qemu_co_mutex_unlock_entry(mutex, self);
 132
 133     assert(mutex->locked == true);
 134     assert(qemu_in_coroutine());
 135
 136     mutex->locked = false;
 137     qemu_co_queue_next(&mutex->queue);
 138
 139     trace_qemu_co_mutex_unlock_return(mutex, self);
 140 }
 141
 142 void qemu_co_rwlock_init(CoRwlock *lock)
 143 {
 144     memset(lock, 0, sizeof(*lock));
 145     qemu_co_queue_init(&lock->queue);
 146 }
 147
 148 void qemu_co_rwlock_rdlock(CoRwlock *lock)
 149 {
 150     while (lock->writer) {
 151         qemu_co_queue_wait(&lock->queue);
 152     }
 153     lock->reader++;
 154 }
 155
 156 void qemu_co_rwlock_unlock(CoRwlock *lock)
 157 {
 158     assert(qemu_in_coroutine());
 159     if (lock->writer) {
 160         lock->writer = false;
 161         qemu_co_queue_restart_all(&lock->queue);
 162     } else {
 163         lock->reader--;
 164         assert(lock->reader >= 0);
 165         /* Wakeup only one waiting writer */
 166         if (!lock->reader) {
 167             qemu_co_queue_next(&lock->queue);
 168         }
 169     }
 170 }
 171
 172 void qemu_co_rwlock_wrlock(CoRwlock *lock)
 173 {
 174     while (lock->writer || lock->reader) {
 175         qemu_co_queue_wait(&lock->queue);
 176     }
 177     lock->writer = true;
 178 }