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Re: [Qemu-devel] [PATCH] dataplane: avoid reentrancy during virtio_blk_d
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] dataplane: avoid reentrancy during virtio_blk_data_plane_stop() |
Date: |
Fri, 18 Jan 2013 16:59:05 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Jan 15, 2013 at 05:19:38PM +0100, Stefan Hajnoczi wrote:
> When dataplane is stopping, the s->vdev->binding->set_host_notifier(...,
> false) call can invoke the virtqueue handler if an ioeventfd
> notification is pending. This causes hw/virtio-blk.c to invoke
> virtio_blk_data_plane_start() before virtio_blk_data_plane_stop()
> returns!
>
> The result is that we try to restart dataplane while trying to stop it
> and the following assertion is raised:
>
> msix_set_mask_notifier: Assertion `!dev->msix_mask_notifier' failed.
>
> Although the code was intended to prevent this scenario, the s->started
> boolean isn't enough. Add s->stopping so that we can postpone clearing
> s->started until we've completely stopped dataplane.
>
> This way, virtqueue handler calls during virtio_blk_data_plane_stop()
> are ignored. When dataplane is legitimately started again later we
> already self-kick ourselves to resume processing.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> hw/dataplane/virtio-blk.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
Applied to my block tree:
https://github.com/stefanha/qemu/commits/block
Stefan