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 5f1fda44882b764d2adcdc4d02a782740db6cbc5..bf515614f131fbd3b5f961756de2757932fd4f85 100644 (file)
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -195,6 +195,7 @@ 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 d752d1c5c8bd9602e68b9824c308449c59747baa..d9f786cf7d5bf5382b494cf3dbf00ad23c9b94fd 100644 (file)
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -99,7 +99,11 @@ 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 63f94134dfce5cf3fd27b1da672ab8c0a5bdc281..7a85ff54a39f33472b33807fdfef2271cd9a0bac 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -819,6 +819,7 @@ 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;
 }
 
 static void tx_credit_callback(unsigned long data)
@@ -1336,8 +1337,10 @@ 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)) {
@@ -1354,6 +1357,7 @@ 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;
        }