From 1680e9063ea28099a1efa8ca11cee069cc7a9bc3 Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Thu, 15 Jul 2010 15:19:12 +0300
Subject: [PATCH] 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>
---
drivers/vhost/net.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2406377a6e5e..2764e0fbf29b 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:
--
2.34.1