Archipelago » qemu

/*

 * QEMU coroutines

 *

 * Copyright IBM, Corp. 2011

 *

 * 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.

 *

 */

#include "trace.h"

#include "qemu-common.h"

#include "qemu/thread.h"

#include "block/coroutine.h"

#include "block/coroutine_int.h"

enum {

    /* Maximum free pool size prevents holding too many freed coroutines */

    POOL_MAX_SIZE = 64,

};

/** Free list to speed up creation */

static QemuMutex pool_lock;

static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);

static unsigned int pool_size;

Coroutine *qemu_coroutine_create(CoroutineEntry *entry)

{

    Coroutine *co = NULL;

    if (CONFIG_COROUTINE_POOL) {

        qemu_mutex_lock(&pool_lock);

        co = QSLIST_FIRST(&pool);

        if (co) {

            QSLIST_REMOVE_HEAD(&pool, pool_next);

            pool_size--;

        }

        qemu_mutex_unlock(&pool_lock);

    }

    if (!co) {

        co = qemu_coroutine_new();

    }

    co->entry = entry;

    QTAILQ_INIT(&co->co_queue_wakeup);

    return co;

}

static void coroutine_delete(Coroutine *co)

{

    if (CONFIG_COROUTINE_POOL) {

        qemu_mutex_lock(&pool_lock);

        if (pool_size < POOL_MAX_SIZE) {

            QSLIST_INSERT_HEAD(&pool, co, pool_next);

            co->caller = NULL;

            pool_size++;

            qemu_mutex_unlock(&pool_lock);

            return;

        }

        qemu_mutex_unlock(&pool_lock);

    }

    qemu_coroutine_delete(co);

}

static void __attribute__((constructor)) coroutine_pool_init(void)

{

    qemu_mutex_init(&pool_lock);

}

static void __attribute__((destructor)) coroutine_pool_cleanup(void)

{

    Coroutine *co;

    Coroutine *tmp;

    QSLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {

        QSLIST_REMOVE_HEAD(&pool, pool_next);

        qemu_coroutine_delete(co);

    }

    qemu_mutex_destroy(&pool_lock);

}

static void coroutine_swap(Coroutine *from, Coroutine *to)

{

    CoroutineAction ret;

    ret = qemu_coroutine_switch(from, to, COROUTINE_YIELD);

    qemu_co_queue_run_restart(to);

    switch (ret) {

    case COROUTINE_YIELD:

        return;

    case COROUTINE_TERMINATE:

        trace_qemu_coroutine_terminate(to);

        coroutine_delete(to);

        return;

    default:

        abort();

    }

}

void qemu_coroutine_enter(Coroutine *co, void *opaque)

{

    Coroutine *self = qemu_coroutine_self();

    trace_qemu_coroutine_enter(self, co, opaque);

    if (co->caller) {

        fprintf(stderr, "Co-routine re-entered recursively\n");

        abort();

    }

    co->caller = self;

    co->entry_arg = opaque;

    coroutine_swap(self, co);

}

void coroutine_fn qemu_coroutine_yield(void)

{

    Coroutine *self = qemu_coroutine_self();

    Coroutine *to = self->caller;

    trace_qemu_coroutine_yield(self, to);

    if (!to) {

        fprintf(stderr, "Co-routine is yielding to no one\n");

        abort();

    }

    self->caller = NULL;

    coroutine_swap(self, to);

}