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Commit dfa523ae authored by Wei Liu's avatar Wei Liu Committed by David S. Miller
Browse files

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: default avatarJean-Louis Dupond <jean-louis@dupond.be>
Signed-off-by: default avatarWei Liu <wei.liu2@citrix.com>
Tested-by: default avatarJean-Louis Dupond <jean-louis@dupond.be>
Reviewed-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 191cdb38

drivers/net/xen-netback/common.h

+1 −0
Original line number Diff line number Diff line
@@ -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;

drivers/net/xen-netback/interface.c

+5 −1
Original line number Diff line number Diff line
@@ -106,6 +106,10 @@ static int xenvif_poll(struct napi_struct *napi, int budget) 


	if (work_done < budget) {

		napi_complete_done(napi, work_done);

		/* 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);

	}

drivers/net/xen-netback/netback.c

+5 −1
Original line number Diff line number Diff line
@@ -180,6 +180,7 @@ 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)
@@ -686,8 +687,10 @@ 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)) {
@@ -702,6 +705,7 @@ 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;

	}