On 03/10/2016 02:51 AM, Fam Zheng wrote:
[...]
> The aio_poll() inside "blk_set_aio_context(s->conf->conf.blk, s->ctx)" looks
> suspicious:
>
> main thread iothread
> ----------------------------------------------------------------------------
> virtio_blk_handle_output()
> virtio_blk_data_plane_start()
> vblk->dataplane_started = true;
> blk_set_aio_context()
> bdrv_set_aio_context()
> bdrv_drain()
> aio_poll()
> <snip...>
> virtio_blk_handle_output()
> /* s->dataplane_started is true */
> !!! -> virtio_blk_handle_request()
> event_notifier_set(ioeventfd)
> aio_poll()
>
> virtio_blk_handle_request()
>
> Christian, could you try the followed patch? The aio_poll above is replaced
> with a "limited aio_poll" that doesn't disptach ioeventfd.
>
> (Note: perhaps moving "vblk->dataplane_started = true;" after
> blk_set_aio_context() also *works around* this.)
>
> ---
>
> diff --git a/block.c b/block.c
> index ba24b8e..e37e8f7 100644
> --- a/block.c
> +++ b/block.c
> @@ -4093,7 +4093,9 @@ void bdrv_attach_aio_context(BlockDriverState *bs,
>
> void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context)
> {
> - bdrv_drain(bs); /* ensure there are no in-flight requests */
> + /* ensure there are no in-flight requests */
> + bdrv_drained_begin(bs);
> + bdrv_drained_end(bs);
>
> bdrv_detach_aio_context(bs);
>
That seems to do the trick.
