Archipelago » qemu

/*

 * 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-common.h"

#include "qemu-coroutine.h"

#include "qemu-coroutine-int.h"

#include "qemu-queue.h"

#include "main-loop.h"

#include "trace.h"

static QTAILQ_HEAD(, Coroutine) unlock_bh_queue =

    QTAILQ_HEAD_INITIALIZER(unlock_bh_queue);

static QEMUBH* unlock_bh;

static void qemu_co_queue_next_bh(void *opaque)

{

    Coroutine *next;

    trace_qemu_co_queue_next_bh();

    while ((next = QTAILQ_FIRST(&unlock_bh_queue))) {

        QTAILQ_REMOVE(&unlock_bh_queue, next, co_queue_next);

        qemu_coroutine_enter(next, NULL);

    }

}

void qemu_co_queue_init(CoQueue *queue)

{

    QTAILQ_INIT(&queue->entries);

    if (!unlock_bh) {

        unlock_bh = qemu_bh_new(qemu_co_queue_next_bh, NULL);

    }

}

void coroutine_fn qemu_co_queue_wait(CoQueue *queue)

{

    Coroutine *self = qemu_coroutine_self();

    QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);

    qemu_coroutine_yield();

    assert(qemu_in_coroutine());

}

bool qemu_co_queue_next(CoQueue *queue)

{

    Coroutine *next;

    next = QTAILQ_FIRST(&queue->entries);

    if (next) {

        QTAILQ_REMOVE(&queue->entries, next, co_queue_next);

        QTAILQ_INSERT_TAIL(&unlock_bh_queue, next, co_queue_next);

        trace_qemu_co_queue_next(next);

        qemu_bh_schedule(unlock_bh);

    }

    return (next != NULL);

}

bool qemu_co_queue_empty(CoQueue *queue)

{

    return (QTAILQ_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;

    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(qemu_in_coroutine());

    mutex->locked = false;

    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)

{

    while (lock->writer) {

        qemu_co_queue_wait(&lock->queue);

    }

    lock->reader++;

}

void qemu_co_rwlock_unlock(CoRwlock *lock)

{

    assert(qemu_in_coroutine());

    if (lock->writer) {

        lock->writer = false;

        while (!qemu_co_queue_empty(&lock->queue)) {

            /*

             * Wakeup every body. This will include some

             * writers too.

             */

            qemu_co_queue_next(&lock->queue);

        }

    } else {

        lock->reader--;

        assert(lock->reader >= 0);

        /* Wakeup only one waiting writer */

        if (!lock->reader) {

            qemu_co_queue_next(&lock->queue);

        }

    }

}

void qemu_co_rwlock_wrlock(CoRwlock *lock)

{

    while (lock->writer || lock->reader) {

        qemu_co_queue_wait(&lock->queue);

    }

    lock->writer = true;

}