Commit 84b6823c authored by Jason Xing's avatar Jason Xing Committed by David S. Miller
Browse files

net: rps: protect last_qtail with rps_input_queue_tail_save() helper 



Removing one unnecessary reader protection and add another writer
protection to finish the locklessly proctection job.

Note: the removed READ_ONCE() is not needed because we only have to protect
the locklessly reader in the different context (rps_may_expire_flow()).

Signed-off-by: default avatarJason Xing <kernelxing@tencent.com>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 00ac0dc3

net/core/dev.c

+4 −4
Original line number Diff line number Diff line
@@ -4507,7 +4507,7 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb, 
		struct netdev_rx_queue *rxqueue;

		struct rps_dev_flow_table *flow_table;

		struct rps_dev_flow *old_rflow;

		u32 flow_id;

		u32 flow_id, head;

		u16 rxq_index;

		int rc;
@@ -4535,8 +4535,8 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb, 
			old_rflow->filter = RPS_NO_FILTER;

	out:

#endif

		rflow->last_qtail =

			READ_ONCE(per_cpu(softnet_data, next_cpu).input_queue_head);

		head = READ_ONCE(per_cpu(softnet_data, next_cpu).input_queue_head);

		rps_input_queue_tail_save(&rflow->last_qtail, head);

	}



	rflow->cpu = next_cpu;
@@ -4619,7 +4619,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb, 
		if (unlikely(tcpu != next_cpu) &&

		    (tcpu >= nr_cpu_ids || !cpu_online(tcpu) ||

		     ((int)(READ_ONCE(per_cpu(softnet_data, tcpu).input_queue_head) -

		      READ_ONCE(rflow->last_qtail))) >= 0)) {

		      rflow->last_qtail)) >= 0)) {

			tcpu = next_cpu;

			rflow = set_rps_cpu(dev, skb, rflow, next_cpu);

		}