coroutines: Locks

#######################################################################

# coroutines

coroutine-obj-y = qemu-coroutine.o

coroutine-obj-y = qemu-coroutine.o qemu-coroutine-lock.o

ifeq ($(CONFIG_UCONTEXT_COROUTINE),y)

coroutine-obj-$(CONFIG_POSIX) += coroutine-ucontext.o

else

    void *entry_arg;

    Coroutine *caller;

    QLIST_ENTRY(Coroutine) pool_next;

    QTAILQ_ENTRY(Coroutine) co_queue_next;

};

Coroutine *qemu_coroutine_new(void);

/*

 * 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 "trace.h"

static QTAILQ_HEAD(, Coroutine) unlock_bh_queue =

    QTAILQ_HEAD_INITIALIZER(unlock_bh_queue);

struct unlock_bh {

    QEMUBH *bh;

};

static void qemu_co_queue_next_bh(void *opaque)

{

    struct unlock_bh *unlock_bh = 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);

    }

    qemu_bh_delete(unlock_bh->bh);

    qemu_free(unlock_bh);

}

void qemu_co_queue_init(CoQueue *queue)

{

    QTAILQ_INIT(&queue->entries);

}

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)

{

    struct unlock_bh *unlock_bh;

    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);

        unlock_bh = qemu_malloc(sizeof(*unlock_bh));

        unlock_bh->bh = qemu_bh_new(qemu_co_queue_next_bh, unlock_bh);

        qemu_bh_schedule(unlock_bh->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);

}

 *

 * Authors:

 *  Stefan Hajnoczi    <stefanha@linux.vnet.ibm.com>

 *  Kevin Wolf         <kwolf@redhat.com>

 *

 * This work is licensed under the terms of the GNU LGPL, version 2 or later.

 * See the COPYING.LIB file in the top-level directory.

#define QEMU_COROUTINE_H

#include <stdbool.h>

#include "qemu-queue.h"

/**

 * Coroutines are a mechanism for stack switching and can be used for

 */

bool qemu_in_coroutine(void);

/**

 * CoQueues are a mechanism to queue coroutines in order to continue executing

 * them later. They provide the fundamental primitives on which coroutine locks

 * are built.

 */

typedef struct CoQueue {

    QTAILQ_HEAD(, Coroutine) entries;

} CoQueue;

/**

 * Initialise a CoQueue. This must be called before any other operation is used

 * on the CoQueue.

 */

void qemu_co_queue_init(CoQueue *queue);

/**

 * Adds the current coroutine to the CoQueue and transfers control to the

 * caller of the coroutine.

 */

void coroutine_fn qemu_co_queue_wait(CoQueue *queue);

/**

 * Restarts the next coroutine in the CoQueue and removes it from the queue.

 *

 * Returns true if a coroutine was restarted, false if the queue is empty.

 */

bool qemu_co_queue_next(CoQueue *queue);

/**

 * Checks if the CoQueue is empty.

 */

bool qemu_co_queue_empty(CoQueue *queue);

/**

 * Provides a mutex that can be used to synchronise coroutines

 */

typedef struct CoMutex {

    bool locked;

    CoQueue queue;

} CoMutex;

/**

 * Initialises a CoMutex. This must be called before any other operation is used

 * on the CoMutex.

 */

void qemu_co_mutex_init(CoMutex *mutex);

/**

 * Locks the mutex. If the lock cannot be taken immediately, control is

 * transferred to the caller of the current coroutine.

 */

void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);

/**

 * Unlocks the mutex and schedules the next coroutine that was waiting for this

 * lock to be run.

 */

void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);

#endif /* QEMU_COROUTINE_H */

disable qemu_coroutine_enter(void *from, void *to, void *opaque) "from %p to %p opaque %p"

disable qemu_coroutine_yield(void *from, void *to) "from %p to %p"

disable qemu_coroutine_terminate(void *co) "self %p"

# qemu-coroutine-lock.c

disable qemu_co_queue_next_bh(void) ""

disable qemu_co_queue_next(void *next) "next %p"

disable qemu_co_mutex_lock_entry(void *mutex, void *self) "mutex %p self %p"

disable qemu_co_mutex_lock_return(void *mutex, void *self) "mutex %p self %p"

disable qemu_co_mutex_unlock_entry(void *mutex, void *self) "mutex %p self %p"

disable qemu_co_mutex_unlock_return(void *mutex, void *self) "mutex %p self %p"