Am 09.12.2020 um 17:51 hat Sergio Lopez geschrieben: > On Mon, Dec 07, 2020 at 04:37:53PM +0100, Kevin Wolf wrote: > > Am 04.12.2020 um 17:53 hat Sergio Lopez geschrieben: > > > On dataplane start, acquire the new AIO context before calling > > > 'blk_set_aio_context', releasing it immediately afterwards. This > > > prevents reaching the AIO context attach/detach notifier functions > > > without having acquired it first. > > > > > > It was also the only place where 'blk_set_aio_context' was called with > > > an unprotected AIO context. > > > > > > Signed-off-by: Sergio Lopez <s...@redhat.com> > > > --- > > > hw/block/dataplane/virtio-blk.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/hw/block/dataplane/virtio-blk.c > > > b/hw/block/dataplane/virtio-blk.c > > > index 37499c5564..034e43cb1f 100644 > > > --- a/hw/block/dataplane/virtio-blk.c > > > +++ b/hw/block/dataplane/virtio-blk.c > > > @@ -214,7 +214,9 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev) > > > vblk->dataplane_started = true; > > > trace_virtio_blk_data_plane_start(s); > > > > > > + aio_context_acquire(s->ctx); > > > r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err); > > > + aio_context_release(s->ctx); > > > > bdrv_set_aio_context_ignore() is documented like this: > > > > * The caller must own the AioContext lock for the old AioContext of bs, > > but it > > * must not own the AioContext lock for new_context (unless new_context is > > the > > * same as the current context of bs). > > Does that rule apply to blk_set_aio_context too?
bdrv_set_aio_context_ignore() is what blk_set_aio_context() calls, so I would say yes. > All use cases I can find in the code are acquiring the new context: > [...] Hm... That's unfortunate. I think the reason why you shouldn't hold it is that the bdrv_drained_begin() call in bdrv_set_aio_context_ignore() could deadlock if you hold the lock of a context that is not the current context of the BlockDriverState. Maybe there are more reasons, I'm not sure. Kevin
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