Commit b89d92f3 authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

block: add aio_wait_bh_oneshot() 



Sometimes it's necessary for the main loop thread to run a BH in an
IOThread and wait for its completion.  This primitive is useful during
startup/shutdown to synchronize and avoid race conditions.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: default avatarFam Zheng <famz@redhat.com>
Acked-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-id: 20180307144205.20619-2-stefanha@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 12c1c7d7

include/block/aio-wait.h

+13 −0
Original line number Diff line number Diff line
@@ -113,4 +113,17 @@ typedef struct { 
 */

void aio_wait_kick(AioWait *wait);



/**

 * aio_wait_bh_oneshot:

 * @ctx: the aio context

 * @cb: the BH callback function

 * @opaque: user data for the BH callback function

 *

 * Run a BH in @ctx and wait for it to complete.

 *

 * Must be called from the main loop thread with @ctx acquired exactly once.

 * Note that main loop event processing may occur.

 */

void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);



#endif /* QEMU_AIO_WAIT */

util/aio-wait.c

+31 −0
Original line number Diff line number Diff line
@@ -38,3 +38,34 @@ void aio_wait_kick(AioWait *wait) 
        aio_bh_schedule_oneshot(qemu_get_aio_context(), dummy_bh_cb, NULL);

    }

}



typedef struct {

    AioWait wait;

    bool done;

    QEMUBHFunc *cb;

    void *opaque;

} AioWaitBHData;



/* Context: BH in IOThread */

static void aio_wait_bh(void *opaque)

{

    AioWaitBHData *data = opaque;



    data->cb(data->opaque);



    data->done = true;

    aio_wait_kick(&data->wait);

}



void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque)

{

    AioWaitBHData data = {

        .cb = cb,

        .opaque = opaque,

    };



    assert(qemu_get_current_aio_context() == qemu_get_aio_context());



    aio_bh_schedule_oneshot(ctx, aio_wait_bh, &data);

    AIO_WAIT_WHILE(&data.wait, ctx, !data.done);

}