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/*

 * QEMU aio implementation

 *

 * Copyright IBM Corp., 2008

 * Copyright Red Hat Inc., 2012

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *  Paolo Bonzini     <pbonzini@redhat.com>

 *

 * This work is licensed under the terms of the GNU GPL, version 2.  See

 * the COPYING file in the top-level directory.

 *

 * Contributions after 2012-01-13 are licensed under the terms of the

 * GNU GPL, version 2 or (at your option) any later version.

 */

#include "qemu-common.h"

#include "block/block.h"

#include "qemu/queue.h"

#include "qemu/sockets.h"

struct AioHandler {

    EventNotifier *e;

    EventNotifierHandler *io_notify;

    AioFlushEventNotifierHandler *io_flush;

    GPollFD pfd;

    int deleted;

    QLIST_ENTRY(AioHandler) node;

};

void aio_set_event_notifier(AioContext *ctx,

                            EventNotifier *e,

                            EventNotifierHandler *io_notify,

                            AioFlushEventNotifierHandler *io_flush)

{

    AioHandler *node;

    QLIST_FOREACH(node, &ctx->aio_handlers, node) {

        if (node->e == e && !node->deleted) {

            break;

        }

    }

    /* Are we deleting the fd handler? */

    if (!io_notify) {

        if (node) {

            g_source_remove_poll(&ctx->source, &node->pfd);

            /* If the lock is held, just mark the node as deleted */

            if (ctx->walking_handlers) {

                node->deleted = 1;

                node->pfd.revents = 0;

            } else {

                /* Otherwise, delete it for real.  We can't just mark it as

                 * deleted because deleted nodes are only cleaned up after

                 * releasing the walking_handlers lock.

                 */

                QLIST_REMOVE(node, node);

                g_free(node);

            }

        }

    } else {

        if (node == NULL) {

            /* Alloc and insert if it's not already there */

            node = g_malloc0(sizeof(AioHandler));

            node->e = e;

            node->pfd.fd = (uintptr_t)event_notifier_get_handle(e);

            node->pfd.events = G_IO_IN;

            QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);

            g_source_add_poll(&ctx->source, &node->pfd);

        }

        /* Update handler with latest information */

        node->io_notify = io_notify;

        node->io_flush = io_flush;

    }

    aio_notify(ctx);

}

bool aio_pending(AioContext *ctx)

{

    AioHandler *node;

    QLIST_FOREACH(node, &ctx->aio_handlers, node) {

        if (node->pfd.revents && node->io_notify) {

            return true;

        }

    }

    return false;

}

bool aio_poll(AioContext *ctx, bool blocking)

{

    AioHandler *node;

    HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];

    bool busy, progress;

    int count;

    progress = false;

    /*

     * If there are callbacks left that have been queued, we need to call then.

     * Do not call select in this case, because it is possible that the caller

     * does not need a complete flush (as is the case for qemu_aio_wait loops).

     */

    if (aio_bh_poll(ctx)) {

        blocking = false;

        progress = true;

    }

    /*

     * Then dispatch any pending callbacks from the GSource.

     *

     * We have to walk very carefully in case qemu_aio_set_fd_handler is

     * called while we're walking.

     */

    node = QLIST_FIRST(&ctx->aio_handlers);

    while (node) {

        AioHandler *tmp;

        ctx->walking_handlers++;

        if (node->pfd.revents && node->io_notify) {

            node->pfd.revents = 0;

            node->io_notify(node->e);

            progress = true;

        }

        tmp = node;

        node = QLIST_NEXT(node, node);

        ctx->walking_handlers--;

        if (!ctx->walking_handlers && tmp->deleted) {

            QLIST_REMOVE(tmp, node);

            g_free(tmp);

        }

    }

    if (progress && !blocking) {

        return true;

    }

    ctx->walking_handlers++;

    /* fill fd sets */

    busy = false;

    count = 0;

    QLIST_FOREACH(node, &ctx->aio_handlers, node) {

        /* If there aren't pending AIO operations, don't invoke callbacks.

         * Otherwise, if there are no AIO requests, qemu_aio_wait() would

         * wait indefinitely.

         */

        if (!node->deleted && node->io_flush) {

            if (node->io_flush(node->e) == 0) {

                continue;

            }

            busy = true;

        }

        if (!node->deleted && node->io_notify) {

            events[count++] = event_notifier_get_handle(node->e);

        }

    }

    ctx->walking_handlers--;

    /* No AIO operations?  Get us out of here */

    if (!busy) {

        return progress;

    }

    /* wait until next event */

    while (count > 0) {

        int timeout = blocking ? INFINITE : 0;

        int ret = WaitForMultipleObjects(count, events, FALSE, timeout);

        /* if we have any signaled events, dispatch event */

        if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {

            break;

        }

        blocking = false;

        /* we have to walk very carefully in case

         * qemu_aio_set_fd_handler is called while we're walking */

        node = QLIST_FIRST(&ctx->aio_handlers);

        while (node) {

            AioHandler *tmp;

            ctx->walking_handlers++;

            if (!node->deleted &&

                event_notifier_get_handle(node->e) == events[ret - WAIT_OBJECT_0] &&

                node->io_notify) {

                node->io_notify(node->e);

                progress = true;

            }

            tmp = node;

            node = QLIST_NEXT(node, node);

            ctx->walking_handlers--;

            if (!ctx->walking_handlers && tmp->deleted) {

                QLIST_REMOVE(tmp, node);

                g_free(tmp);

            }

        }

        /* Try again, but only call each handler once.  */

        events[ret - WAIT_OBJECT_0] = events[--count];

    }

    assert(progress || busy);

    return true;

}