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>
OraBug: 26662731

(cherry picked from commit dfa523ae9f2542bee4cddaea37b3be3e157f6e6b)
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
Conflicts:
	drivers/net/xen-netback/interface.c
	(Upstream's code used napi_complete_done())

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 2c2f98fa575ba73dd3e30277cf857df996e1c0cd..7c4d2e133411f340c5828d53ce2018706d913528 100644 (file)
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -223,6 +223,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
        unsigned long   remaining_credit;
        struct timer_list credit_timeout;
        u64 credit_window_start;
+       bool rate_limited;
 
        /* Permanent grant mappings */
        struct xenvif_grant_mapping grant;

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 77db33fea67c1f052d91f25e443a7268be700d5b..461b764f0567c6e133f5c0c3fdb7b7bd47da7217 100644 (file)
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -108,7 +108,11 @@ 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 d988c2d15af4166844d46e04e2989bf9b4b66130..faf9272290c4d69f6b6f201aed949327d9b95e5e 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -194,6 +194,7 @@ 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)
@@ -788,8 +789,10 @@ 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)) {
@@ -804,6 +807,7 @@ 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;
        }