Shannon Nelson
2023-Jul-18 19:09 UTC
[PATCH RFC net] virtio-net: add timeout for virtnet_send_command()
When trying to talk to a device that has gone out to lunch, the
virtnet_send_command() will sit and spin forever, causing a soft
lockup and eventually crashing the kernel. Add a limit to the
spin and return false if we hit the timeout. The 2 second time
limit seems a bit arbitrary, but a reasonable place to start.
This is a little more brute force than Jason's suggestions in [1],
but at least prevents the soft lockups and eventual kernel crash
that we were seeing in testing.
[1]: https://lore.kernel.org/netdev/20230524081842.3060-1-jasowang at
redhat.com/
Fixes: 2a41f71d3bd9 ("virtio_net: Add a virtqueue for outbound control
commands")
Signed-off-by: Shannon Nelson <shannon.nelson at amd.com>
---
drivers/net/virtio_net.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0db14f6b87d3..c3bf1c9f3244 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2264,6 +2264,8 @@ static bool virtnet_send_command(struct virtnet_info *vi,
u8 class, u8 cmd,
{
struct scatterlist *sgs[4], hdr, stat;
unsigned out_num = 0, tmp;
+ unsigned long deadline;
+ bool timeout;
int ret;
/* Caller should know better */
@@ -2297,11 +2299,16 @@ 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.
*/
+ deadline = jiffies + 2 * HZ;
+ timeout = false;
while (!virtqueue_get_buf(vi->cvq, &tmp) &&
- !virtqueue_is_broken(vi->cvq))
+ !virtqueue_is_broken(vi->cvq) &&
+ !timeout) {
cpu_relax();
+ timeout = time_after(jiffies, deadline);
+ }
- return vi->ctrl->status == VIRTIO_NET_OK;
+ return vi->ctrl->status == VIRTIO_NET_OK && !timeout;
}
static int virtnet_set_mac_address(struct net_device *dev, void *p)
--
2.17.1