xen-netback: correctly schedule rate-limited queues

[ Upstream commit dfa523ae9f2542bee4cddaea37b3be3e157f6e6b ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 3ce1f7da864742a2aa1fe268ffd440b09764ea05..cb7365bdf6e0031f4ec48d5334df5f5721131c64 100644 (file)
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -199,6 +199,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
        unsigned long   remaining_credit;
        struct timer_list credit_timeout;
        u64 credit_window_start;
+       bool rate_limited;
 
        /* Statistics */
        struct xenvif_stats stats;

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index b009d7966b46f272872a30832e12d92235acd6c0..5bfaf5578810d20faf20c66ef400e2e52c4ba60e 100644 (file)
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -105,7 +105,11 @@ static int xenvif_poll(struct napi_struct *napi, int budget)
 
        if (work_done < budget) {
                napi_complete(napi);
-               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;

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 47b481095d773fc9aaf1bf0045bdcee5bc89e3cc..d9b5b73c35a026308e7c339344f30b5f10b6126d 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -179,6 +179,7 @@ static void tx_add_credit(struct xenvif_queue *queue)
                max_credit = ULONG_MAX; /* wrapped: clamp to ULONG_MAX */
 
        queue->remaining_credit = min(max_credit, max_burst);
+       queue->rate_limited = false;
 }
 
 void xenvif_tx_credit_callback(unsigned long data)
@@ -685,8 +686,10 @@ static bool tx_credit_exceeded(struct xenvif_queue *queue, unsigned size)
                msecs_to_jiffies(queue->credit_usec / 1000);
 
        /* Timer could already be pending in rare cases. */
-       if (timer_pending(&queue->credit_timeout))
+       if (timer_pending(&queue->credit_timeout)) {
+               queue->rate_limited = true;
                return true;
+       }
 
        /* Passed the point where we can replenish credit? */
        if (time_after_eq64(now, next_credit)) {
@@ -701,6 +704,7 @@ static bool tx_credit_exceeded(struct xenvif_queue *queue, unsigned size)
                mod_timer(&queue->credit_timeout,
                          next_credit);
                queue->credit_window_start = next_credit;
+               queue->rate_limited = true;
 
                return true;
        }