Commit ecc1a5c7 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

test-bdrv-drain: Test nested poll in bdrv_drain_poll_top_level() 



This is a regression test for a deadlock that could occur in callbacks
called from the aio_poll() in bdrv_drain_poll_top_level(). The
AioContext lock wasn't released and therefore would be taken a second
time in the callback. This would cause a possible AIO_WAIT_WHILE() in
the callback to hang.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarFam Zheng <famz@redhat.com>
parent 4cf077b5

tests/test-bdrv-drain.c

+13 −0
Original line number Diff line number Diff line
@@ -636,6 +636,17 @@ static void test_iothread_aio_cb(void *opaque, int ret) 
    qemu_event_set(&done_event);

}



static void test_iothread_main_thread_bh(void *opaque)

{

    struct test_iothread_data *data = opaque;



    /* Test that the AioContext is not yet locked in a random BH that is

     * executed during drain, otherwise this would deadlock. */

    aio_context_acquire(bdrv_get_aio_context(data->bs));

    bdrv_flush(data->bs);

    aio_context_release(bdrv_get_aio_context(data->bs));

}



/*

 * Starts an AIO request on a BDS that runs in the AioContext of iothread 1.

 * The request involves a BH on iothread 2 before it can complete.
@@ -705,6 +716,8 @@ static void test_iothread_common(enum drain_type drain_type, int drain_thread) 
            aio_context_acquire(ctx_a);

        }



        aio_bh_schedule_oneshot(ctx_a, test_iothread_main_thread_bh, &data);



        /* The request is running on the IOThread a. Draining its block device

         * will make sure that it has completed as far as the BDS is concerned,

         * but the drain in this thread can continue immediately after