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| author | David S. Miller <davem@davemloft.net> | 2024-04-19 11:38:04 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2024-04-19 11:38:04 +0100 |
| commit | 78e8311a85fec3902d87093f67a882bcca1a3ae9 (patch) | |
| tree | 48669426a813531a30360209f49f26de7e5e5f56 | |
| parent | 00ac0dc347dc2d557ba7a1da289708943a3ac5a7 (diff) | |
| parent | f7b60cce847036f4a639d44c675553a564d8e876 (diff) | |
| download | mptcp_net-next-78e8311a85fec3902d87093f67a882bcca1a3ae9.tar.gz | |
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>
| -rw-r--r-- | net/core/dev.c | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index f6c6e494f0a91e..8bdc59074b29c2 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -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; @@ -4530,16 +4530,16 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb, goto out; old_rflow = rflow; rflow = &flow_table->flows[flow_id]; - rflow->filter = rc; - if (old_rflow->filter == rflow->filter) - old_rflow->filter = RPS_NO_FILTER; + WRITE_ONCE(rflow->filter, rc); + if (old_rflow->filter == rc) + WRITE_ONCE(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; + WRITE_ONCE(rflow->cpu, next_cpu); return rflow; } @@ -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); } @@ -4672,7 +4672,7 @@ bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index, if (flow_table && flow_id <= flow_table->mask) { rflow = &flow_table->flows[flow_id]; cpu = READ_ONCE(rflow->cpu); - if (rflow->filter == filter_id && cpu < nr_cpu_ids && + if (READ_ONCE(rflow->filter) == filter_id && cpu < nr_cpu_ids && ((int)(READ_ONCE(per_cpu(softnet_data, cpu).input_queue_head) - READ_ONCE(rflow->last_qtail)) < (int)(10 * flow_table->mask))) |