On Thu, Jul 15, 2010 at 03:19:12PM +0300, Michael S. Tsirkin wrote:
> We flush under vq mutex when changing backends.
> This creates a deadlock as workqueue being flushed
> needs this lock as well.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=612421
>
> Drop the vq mutex before flush: we have the device mutex
> which is sufficient to prevent another ioctl from touching
> the vq.
>
> Signed-off-by: Michael S. Tsirkin <[email protected]>
Dave, just to clarify, I'll send pull request to merge it through my tree,
there's no need for you to bother with this.
> ---
> drivers/vhost/net.c | 5 +++++
> 1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 28d7786..50df58e6 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -534,11 +534,16 @@ static long vhost_net_set_backend(struct vhost_net *n,
> unsigned index, int fd)
> rcu_assign_pointer(vq->private_data, sock);
> vhost_net_enable_vq(n, vq);
> done:
> + mutex_unlock(&vq->mutex);
> +
> if (oldsock) {
> vhost_net_flush_vq(n, index);
> fput(oldsock->file);
> }
>
> + mutex_unlock(&n->dev.mutex);
> + return 0;
> +
> err_vq:
> mutex_unlock(&vq->mutex);
> err:
> --
> 1.7.2.rc0.14.g41c1c
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