Re: [PATCH] vhost-net: avoid flush under lock
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2010-07-15 12:43:48
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 <mst@redhat.com>
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.
quoted hunk ↗ jump to hunk
--- 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