[PATCH RFC 3/7] virtio_net: avoid cpu_relax() call loop in case virtqueue is broken

[Heinz Graalfs <graalfs@linux.vnet.ibm.com>]

A virtqueue_kick() call to notify a host might fail in case the network
device was hot-unplugged.
Spinning for a response for a VIRTIO_NET_CTRL_VLAN_DEL command response
will end up in a never ending loop waiting for a response.
This patch avoids the cpu_relax() loop in case the virtqueue is flagged
as broken.

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
---
 drivers/net/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ab2e5d0..57f5f13 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -800,8 +800,10 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 
 	/* Spin for a response, the kick causes an ioport write, trapping
 	 * into the hypervisor, so the request should be handled immediately.
+	 * Do not wait for a response in case the virtqueue is 'broken'.
 	 */
-	while (!virtqueue_get_buf(vi->cvq, &tmp))
+	while (!virtqueue_get_buf(vi->cvq, &tmp)
+		&& !virtqueue_is_broken(vi->cvq))
 		cpu_relax();
 
 	return status == VIRTIO_NET_OK;
-- 
1.8.3.1