From: Michael S. Tsirkin <mst@redhat.com>
Date: Thu, 15 Jul 2010 12:19:12 +0000 (+0300)
Subject: vhost-net: avoid flush under lock
X-Git-Tag: v2.6.35-rc6~15^2~5^2~1
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=1680e9063ea28099a1efa8ca11cee069cc7a9bc3;p=~emulex%2Finfiniband.git

vhost-net: avoid flush under lock

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>
---

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2406377a6e5..2764e0fbf29 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: