Archipelago » qemu

/*

 * QEMU System Emulator

 *

 * Copyright (c) 2003-2008 Fabrice Bellard

 *

 * 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 "block/aio.h"

#include "block/thread-pool.h"

#include "qemu/main-loop.h"

/***********************************************************/

/* bottom halves (can be seen as timers which expire ASAP) */

struct QEMUBH {

    AioContext *ctx;

    QEMUBHFunc *cb;

    void *opaque;

    QEMUBH *next;

    bool scheduled;

    bool idle;

    bool deleted;

};

QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)

{

    QEMUBH *bh;

    bh = g_malloc0(sizeof(QEMUBH));

    bh->ctx = ctx;

    bh->cb = cb;

    bh->opaque = opaque;

    qemu_mutex_lock(&ctx->bh_lock);

    bh->next = ctx->first_bh;

    /* Make sure that the members are ready before putting bh into list */

    smp_wmb();

    ctx->first_bh = bh;

    qemu_mutex_unlock(&ctx->bh_lock);

    return bh;

}

/* Multiple occurrences of aio_bh_poll cannot be called concurrently */

int aio_bh_poll(AioContext *ctx)

{

    QEMUBH *bh, **bhp, *next;

    int ret;

    ctx->walking_bh++;

    ret = 0;

    for (bh = ctx->first_bh; bh; bh = next) {

        /* Make sure that fetching bh happens before accessing its members */

        smp_read_barrier_depends();

        next = bh->next;

        if (!bh->deleted && bh->scheduled) {

            bh->scheduled = 0;

            /* Paired with write barrier in bh schedule to ensure reading for

             * idle & callbacks coming after bh's scheduling.

             */

            smp_rmb();

            if (!bh->idle)

                ret = 1;

            bh->idle = 0;

            bh->cb(bh->opaque);

        }

    }

    ctx->walking_bh--;

    /* remove deleted bhs */

    if (!ctx->walking_bh) {

        qemu_mutex_lock(&ctx->bh_lock);

        bhp = &ctx->first_bh;

        while (*bhp) {

            bh = *bhp;

            if (bh->deleted) {

                *bhp = bh->next;

                g_free(bh);

            } else {

                bhp = &bh->next;

            }

        }

        qemu_mutex_unlock(&ctx->bh_lock);

    }

    return ret;

}

void qemu_bh_schedule_idle(QEMUBH *bh)

{

    if (bh->scheduled)

        return;

    bh->idle = 1;

    /* Make sure that idle & any writes needed by the callback are done

     * before the locations are read in the aio_bh_poll.

     */

    smp_wmb();

    bh->scheduled = 1;

}

void qemu_bh_schedule(QEMUBH *bh)

{

    if (bh->scheduled)

        return;

    bh->idle = 0;

    /* Make sure that idle & any writes needed by the callback are done

     * before the locations are read in the aio_bh_poll.

     */

    smp_wmb();

    bh->scheduled = 1;

    aio_notify(bh->ctx);

}

/* This func is async.

 */

void qemu_bh_cancel(QEMUBH *bh)

{

    bh->scheduled = 0;

}

/* This func is async.The bottom half will do the delete action at the finial

 * end.

 */

void qemu_bh_delete(QEMUBH *bh)

{

    bh->scheduled = 0;

    bh->deleted = 1;

}

static gboolean

aio_ctx_prepare(GSource *source, gint    *timeout)

{

    AioContext *ctx = (AioContext *) source;

    QEMUBH *bh;

    for (bh = ctx->first_bh; bh; bh = bh->next) {

        if (!bh->deleted && bh->scheduled) {

            if (bh->idle) {

                /* idle bottom halves will be polled at least

                 * every 10ms */

                *timeout = 10;

            } else {

                /* non-idle bottom halves will be executed

                 * immediately */

                *timeout = 0;

                return true;

            }

        }

    }

    return false;

}

static gboolean

aio_ctx_check(GSource *source)

{

    AioContext *ctx = (AioContext *) source;

    QEMUBH *bh;

    for (bh = ctx->first_bh; bh; bh = bh->next) {

        if (!bh->deleted && bh->scheduled) {

            return true;

        }

    }

    return aio_pending(ctx);

}

static gboolean

aio_ctx_dispatch(GSource     *source,

                 GSourceFunc  callback,

                 gpointer     user_data)

{

    AioContext *ctx = (AioContext *) source;

    assert(callback == NULL);

    aio_poll(ctx, false);

    return true;

}

static void

aio_ctx_finalize(GSource     *source)

{

    AioContext *ctx = (AioContext *) source;

    thread_pool_free(ctx->thread_pool);

    aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);

    event_notifier_cleanup(&ctx->notifier);

    qemu_mutex_destroy(&ctx->bh_lock);

    g_array_free(ctx->pollfds, TRUE);

}

static GSourceFuncs aio_source_funcs = {

    aio_ctx_prepare,

    aio_ctx_check,

    aio_ctx_dispatch,

    aio_ctx_finalize

};

GSource *aio_get_g_source(AioContext *ctx)

{

    g_source_ref(&ctx->source);

    return &ctx->source;

}

ThreadPool *aio_get_thread_pool(AioContext *ctx)

{

    if (!ctx->thread_pool) {

        ctx->thread_pool = thread_pool_new(ctx);

    }

    return ctx->thread_pool;

}

void aio_notify(AioContext *ctx)

{

    event_notifier_set(&ctx->notifier);

}

AioContext *aio_context_new(void)

{

    AioContext *ctx;

    ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));

    ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));

    ctx->thread_pool = NULL;

    qemu_mutex_init(&ctx->bh_lock);

    event_notifier_init(&ctx->notifier, false);

    aio_set_event_notifier(ctx, &ctx->notifier, 

                           (EventNotifierHandler *)

                           event_notifier_test_and_clear, NULL);

    return ctx;

}

void aio_context_ref(AioContext *ctx)

{

    g_source_ref(&ctx->source);

}

void aio_context_unref(AioContext *ctx)

{

    g_source_unref(&ctx->source);

}