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Merge branch 'net-rps-lockless'
Jason Xing says: ==================== locklessly protect left members in struct rps_dev_flow From: Jason Xing <kernelxing@tencent.com> Since Eric did a more complicated locklessly change to last_qtail member[1] in struct rps_dev_flow, the left members are easier to change as the same. One thing important I would like to share by qooting Eric: "rflow is located in rxqueue->rps_flow_table, it is thus private to current thread. Only one cpu can service an RX queue at a time." So we only pay attention to the reader in the rps_may_expire_flow() and writer in the set_rps_cpu(). They are in the two different contexts. [1]: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=3b4cf29bdab v3 Link: https://lore.kernel.org/all/20240417062721.45652-1-kerneljasonxing@gmail.com/ 1. adjust the protection in a right way (Eric) v2 1. fix passing wrong type qtail. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
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commit
78e8311a85
@ -4507,7 +4507,7 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
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struct netdev_rx_queue *rxqueue;
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struct rps_dev_flow_table *flow_table;
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struct rps_dev_flow *old_rflow;
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u32 flow_id;
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u32 flow_id, head;
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u16 rxq_index;
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int rc;
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@ -4530,16 +4530,16 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
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goto out;
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old_rflow = rflow;
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rflow = &flow_table->flows[flow_id];
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rflow->filter = rc;
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if (old_rflow->filter == rflow->filter)
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old_rflow->filter = RPS_NO_FILTER;
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WRITE_ONCE(rflow->filter, rc);
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if (old_rflow->filter == rc)
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WRITE_ONCE(old_rflow->filter, RPS_NO_FILTER);
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out:
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#endif
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rflow->last_qtail =
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READ_ONCE(per_cpu(softnet_data, next_cpu).input_queue_head);
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head = READ_ONCE(per_cpu(softnet_data, next_cpu).input_queue_head);
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rps_input_queue_tail_save(&rflow->last_qtail, head);
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}
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rflow->cpu = next_cpu;
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WRITE_ONCE(rflow->cpu, next_cpu);
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return rflow;
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}
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@ -4619,7 +4619,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
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if (unlikely(tcpu != next_cpu) &&
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(tcpu >= nr_cpu_ids || !cpu_online(tcpu) ||
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((int)(READ_ONCE(per_cpu(softnet_data, tcpu).input_queue_head) -
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READ_ONCE(rflow->last_qtail))) >= 0)) {
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rflow->last_qtail)) >= 0)) {
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tcpu = next_cpu;
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rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
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}
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@ -4672,7 +4672,7 @@ bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index,
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if (flow_table && flow_id <= flow_table->mask) {
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rflow = &flow_table->flows[flow_id];
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cpu = READ_ONCE(rflow->cpu);
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if (rflow->filter == filter_id && cpu < nr_cpu_ids &&
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if (READ_ONCE(rflow->filter) == filter_id && cpu < nr_cpu_ids &&
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((int)(READ_ONCE(per_cpu(softnet_data, cpu).input_queue_head) -
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READ_ONCE(rflow->last_qtail)) <
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(int)(10 * flow_table->mask)))
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