qemu/util/qemu-coroutine-lock.c
Paolo Bonzini a9d9235567 coroutine-lock: reschedule coroutine on the AioContext it was running on
As a small step towards the introduction of multiqueue, we want
coroutines to remain on the same AioContext that started them,
unless they are moved explicitly with e.g. aio_co_schedule.  This patch
avoids that coroutines switch AioContext when they use a CoMutex.
For now it does not make much of a difference, because the CoMutex
is not thread-safe and the AioContext itself is used to protect the
CoMutex from concurrent access.  However, this is going to change.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 20170213135235.12274-9-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2017-02-21 11:14:08 +00:00

201 lines
5.1 KiB
C

/*
* coroutine queues and locks
*
* Copyright (c) 2011 Kevin Wolf <kwolf@redhat.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qemu-common.h"
#include "qemu/coroutine.h"
#include "qemu/coroutine_int.h"
#include "qemu/queue.h"
#include "block/aio.h"
#include "trace.h"
void qemu_co_queue_init(CoQueue *queue)
{
QSIMPLEQ_INIT(&queue->entries);
}
void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
{
Coroutine *self = qemu_coroutine_self();
QSIMPLEQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
qemu_coroutine_yield();
assert(qemu_in_coroutine());
}
/**
* qemu_co_queue_run_restart:
*
* Enter each coroutine that was previously marked for restart by
* qemu_co_queue_next() or qemu_co_queue_restart_all(). This function is
* invoked by the core coroutine code when the current coroutine yields or
* terminates.
*/
void qemu_co_queue_run_restart(Coroutine *co)
{
Coroutine *next;
trace_qemu_co_queue_run_restart(co);
while ((next = QSIMPLEQ_FIRST(&co->co_queue_wakeup))) {
QSIMPLEQ_REMOVE_HEAD(&co->co_queue_wakeup, co_queue_next);
qemu_coroutine_enter(next);
}
}
static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
{
Coroutine *next;
if (QSIMPLEQ_EMPTY(&queue->entries)) {
return false;
}
while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
aio_co_wake(next);
if (single) {
break;
}
}
return true;
}
bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
{
assert(qemu_in_coroutine());
return qemu_co_queue_do_restart(queue, true);
}
void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue)
{
assert(qemu_in_coroutine());
qemu_co_queue_do_restart(queue, false);
}
bool qemu_co_enter_next(CoQueue *queue)
{
Coroutine *next;
next = QSIMPLEQ_FIRST(&queue->entries);
if (!next) {
return false;
}
QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
qemu_coroutine_enter(next);
return true;
}
bool qemu_co_queue_empty(CoQueue *queue)
{
return QSIMPLEQ_FIRST(&queue->entries) == NULL;
}
void qemu_co_mutex_init(CoMutex *mutex)
{
memset(mutex, 0, sizeof(*mutex));
qemu_co_queue_init(&mutex->queue);
}
void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex)
{
Coroutine *self = qemu_coroutine_self();
trace_qemu_co_mutex_lock_entry(mutex, self);
while (mutex->locked) {
qemu_co_queue_wait(&mutex->queue);
}
mutex->locked = true;
mutex->holder = self;
self->locks_held++;
trace_qemu_co_mutex_lock_return(mutex, self);
}
void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex)
{
Coroutine *self = qemu_coroutine_self();
trace_qemu_co_mutex_unlock_entry(mutex, self);
assert(mutex->locked == true);
assert(mutex->holder == self);
assert(qemu_in_coroutine());
mutex->locked = false;
mutex->holder = NULL;
self->locks_held--;
qemu_co_queue_next(&mutex->queue);
trace_qemu_co_mutex_unlock_return(mutex, self);
}
void qemu_co_rwlock_init(CoRwlock *lock)
{
memset(lock, 0, sizeof(*lock));
qemu_co_queue_init(&lock->queue);
}
void qemu_co_rwlock_rdlock(CoRwlock *lock)
{
Coroutine *self = qemu_coroutine_self();
while (lock->writer) {
qemu_co_queue_wait(&lock->queue);
}
lock->reader++;
self->locks_held++;
}
void qemu_co_rwlock_unlock(CoRwlock *lock)
{
Coroutine *self = qemu_coroutine_self();
assert(qemu_in_coroutine());
if (lock->writer) {
lock->writer = false;
qemu_co_queue_restart_all(&lock->queue);
} else {
lock->reader--;
assert(lock->reader >= 0);
/* Wakeup only one waiting writer */
if (!lock->reader) {
qemu_co_queue_next(&lock->queue);
}
}
self->locks_held--;
}
void qemu_co_rwlock_wrlock(CoRwlock *lock)
{
Coroutine *self = qemu_coroutine_self();
while (lock->writer || lock->reader) {
qemu_co_queue_wait(&lock->queue);
}
lock->writer = true;
self->locks_held++;
}