xen-netback: correctly schedule rate-limited queues

Add a flag to indicate if a queue is rate-limited. Test the flag in
NAPI poll handler and avoid rescheduling the queue if true, otherwise
we risk locking up the host. The rescheduling will be done in the
timer callback function.

Reported-by: Jean-Louis Dupond <jean-louis@dupond.be>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Tested-by: Jean-Louis Dupond <jean-louis@dupond.be>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 8397f6c92451..e322a862ddfe 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -106,7 +106,11 @@ static int xenvif_poll(struct napi_struct *napi, int budget)
 
         if (work_done < budget) {
                 napi_complete_done(napi, work_done);
-                xenvif_napi_schedule_or_enable_events(queue);
+                /* If the queue is rate-limited, it shall be
+                 * rescheduled in the timer callback.
+                 */
+                if (likely(!queue->rate_limited))
+                        xenvif_napi_schedule_or_enable_events(queue);
         }
 
         return work_done;