From: Michael S. Tsirkin on
We flush under vq mutex when changing backends.
This creates a deadlock as workqueue being flushed
needs this lock as well.

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(a)>
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);
+ mutex_unlock(&vq->mutex);
if (oldsock) {
vhost_net_flush_vq(n, index);

+ mutex_unlock(&n->dev.mutex);
+ return 0;
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