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Message-Id: <20240418073603.99336-2-kerneljasonxing@gmail.com>
Date: Thu, 18 Apr 2024 15:36:01 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
davem@...emloft.net,
horms@...nel.org
Cc: netdev@...r.kernel.org,
kerneljasonxing@...il.com,
Jason Xing <kernelxing@...cent.com>
Subject: [PATCH net-next v3 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper
From: Jason Xing <kernelxing@...cent.com>
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: Jason Xing <kernelxing@...cent.com>
---
net/core/dev.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 854a3a28a8d8..58e0da91bfef 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4501,7 +4501,7 @@ 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;
@@ -4529,8 +4529,8 @@ 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;
@@ -4613,7 +4613,7 @@ 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);
}
--
2.37.3
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