Archipelago » qemu

/*

 * QEMU aio implementation

 *

 * Copyright IBM, Corp. 2008

 *

 * Authors:

 *  Anthony Liguori   <aliguori@us.ibm.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_socket.h"

struct AioHandler

{

    GPollFD pfd;

    IOHandler *io_read;

    IOHandler *io_write;

    AioFlushHandler *io_flush;

    int deleted;

    void *opaque;

    QLIST_ENTRY(AioHandler) node;

};

static AioHandler *find_aio_handler(AioContext *ctx, int fd)

{

    AioHandler *node;

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

        if (node->pfd.fd == fd)

            if (!node->deleted)

                return node;

    }

    return NULL;

}

void aio_set_fd_handler(AioContext *ctx,

                        int fd,

                        IOHandler *io_read,

                        IOHandler *io_write,

                        AioFlushHandler *io_flush,

                        void *opaque)

{

    AioHandler *node;

    node = find_aio_handler(ctx, fd);

    /* Are we deleting the fd handler? */

    if (!io_read && !io_write) {

        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->pfd.fd = fd;

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

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

        }

        /* Update handler with latest information */

        node->io_read = io_read;

        node->io_write = io_write;

        node->io_flush = io_flush;

        node->opaque = opaque;

        node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP : 0);

        node->pfd.events |= (io_write ? G_IO_OUT : 0);

    }

    aio_notify(ctx);

}

void aio_set_event_notifier(AioContext *ctx,

                            EventNotifier *notifier,

                            EventNotifierHandler *io_read,

                            AioFlushEventNotifierHandler *io_flush)

{

    aio_set_fd_handler(ctx, event_notifier_get_fd(notifier),

                       (IOHandler *)io_read, NULL,

                       (AioFlushHandler *)io_flush, notifier);

}

bool aio_pending(AioContext *ctx)

{

    AioHandler *node;

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

        int revents;

        /*

         * FIXME: right now we cannot get G_IO_HUP and G_IO_ERR because

         * main-loop.c is still select based (due to the slirp legacy).

         * If main-loop.c ever switches to poll, G_IO_ERR should be

         * tested too.  Dispatching G_IO_ERR to both handlers should be

         * okay, since handlers need to be ready for spurious wakeups.

         */

        revents = node->pfd.revents & node->pfd.events;

        if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) {

            return true;

        }

        if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) {

            return true;

        }

    }

    return false;

}

bool aio_poll(AioContext *ctx, bool blocking)

{

    static struct timeval tv0;

    AioHandler *node;

    fd_set rdfds, wrfds;

    int max_fd = -1;

    int ret;

    bool busy, progress;

    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;

        int revents;

        ctx->walking_handlers++;

        revents = node->pfd.revents & node->pfd.events;

        node->pfd.revents = 0;

        /* See comment in aio_pending.  */

        if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) {

            node->io_read(node->opaque);

            progress = true;

        }

        if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) {

            node->io_write(node->opaque);

            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++;

    FD_ZERO(&rdfds);

    FD_ZERO(&wrfds);

    /* fill fd sets */

    busy = false;

    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->opaque) == 0) {

                continue;

            }

            busy = true;

        }

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

            FD_SET(node->pfd.fd, &rdfds);

            max_fd = MAX(max_fd, node->pfd.fd + 1);

        }

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

            FD_SET(node->pfd.fd, &wrfds);

            max_fd = MAX(max_fd, node->pfd.fd + 1);

        }

    }

    ctx->walking_handlers--;

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

    if (!busy) {

        return progress;

    }

    /* wait until next event */

    ret = select(max_fd, &rdfds, &wrfds, NULL, blocking ? NULL : &tv0);

    /* if we have any readable fds, dispatch event */

    if (ret > 0) {

        /* 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 &&

                FD_ISSET(node->pfd.fd, &rdfds) &&

                node->io_read) {

                node->io_read(node->opaque);

                progress = true;

            }

            if (!node->deleted &&

                FD_ISSET(node->pfd.fd, &wrfds) &&

                node->io_write) {

                node->io_write(node->opaque);

                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);

            }

        }

    }

    return progress;

}