On Thu, Feb 12, 2015 at 01:21:00PM +0800, Fam Zheng wrote: > Even if the caller has the old #AioContext, there can be a deadlock, due > to the leading bdrv_drain_all: > > Suppose there are three io threads (a, b, c) with each owning a BDS > (bds_a, bds_b, bds_c), and a and b want to move their own BDS to c at > the same time: > > iothread a iothread b > -------------------------------------------------------------------------- > bdrv_set_aio_context(bds_a, c) bdrv_set_aio_context(bds_b, c) > -> bdrv_drain_all() -> bdrv_drain_all() > -> acquire a (OK, already has) -> acquire a (blocked) > -> acquire b (blocked) -> acquire b > -> acquire c -> acquire c > > Current caller of bdrv_set_aio_context outside BQL is > virtio-scsi-dataplane, which will be fixed in the next patches. > > Signed-off-by: Fam Zheng <f...@redhat.com> > --- > include/block/block.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
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