* [PATCH net-next 0/3] locklessly protect left members in struct rps_dev_flow
@ 2024-04-16 7:42 Jason Xing
2024-04-16 7:42 ` [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper Jason Xing
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Jason Xing @ 2024-04-16 7:42 UTC (permalink / raw)
To: edumazet, kuba, pabeni, davem, horms; +Cc: netdev, kerneljasonxing, Jason Xing
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.
[1]:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=3b4cf29bdab
Jason Xing (3):
net: rps: protect last_qtail with rps_input_queue_tail_save() helper
net: rps: protect filter locklessly
net: rps: locklessly access rflow->cpu
net/core/dev.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--
2.37.3
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper
2024-04-16 7:42 [PATCH net-next 0/3] locklessly protect left members in struct rps_dev_flow Jason Xing
@ 2024-04-16 7:42 ` Jason Xing
2024-04-17 0:26 ` Jason Xing
2024-04-16 7:42 ` [PATCH net-next 2/3] net: rps: protect filter locklessly Jason Xing
2024-04-16 7:42 ` [PATCH net-next 3/3] net: rps: locklessly access rflow->cpu Jason Xing
2 siblings, 1 reply; 5+ messages in thread
From: Jason Xing @ 2024-04-16 7:42 UTC (permalink / raw)
To: edumazet, kuba, pabeni, davem, horms; +Cc: netdev, kerneljasonxing, Jason Xing
From: Jason Xing <kernelxing@tencent.com>
Only one left place should be proctected locklessly. This patch made it.
Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
net/core/dev.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 854a3a28a8d8..cd97eeae8218 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;
--
2.37.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH net-next 2/3] net: rps: protect filter locklessly
2024-04-16 7:42 [PATCH net-next 0/3] locklessly protect left members in struct rps_dev_flow Jason Xing
2024-04-16 7:42 ` [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper Jason Xing
@ 2024-04-16 7:42 ` Jason Xing
2024-04-16 7:42 ` [PATCH net-next 3/3] net: rps: locklessly access rflow->cpu Jason Xing
2 siblings, 0 replies; 5+ messages in thread
From: Jason Xing @ 2024-04-16 7:42 UTC (permalink / raw)
To: edumazet, kuba, pabeni, davem, horms; +Cc: netdev, kerneljasonxing, Jason Xing
From: Jason Xing <kernelxing@tencent.com>
As we can see, rflow->filter can be written/read concurrently, so
lockless access is needed.
Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
I'm not very sure if the READ_ONCE in set_rps_cpu() is useful. I
scaned/checked the codes and found no lock can prevent multiple
threads from calling set_rps_cpu() and handling the same flow
simultaneously. The same question still exists in patch [3/3].
---
net/core/dev.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index cd97eeae8218..6892682f9cbf 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4524,8 +4524,8 @@ 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)
+ WRITE_ONCE(rflow->filter, rc);
+ if (old_rflow->filter == READ_ONCE(rflow->filter))
old_rflow->filter = RPS_NO_FILTER;
out:
#endif
@@ -4666,7 +4666,7 @@ 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)))
--
2.37.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH net-next 3/3] net: rps: locklessly access rflow->cpu
2024-04-16 7:42 [PATCH net-next 0/3] locklessly protect left members in struct rps_dev_flow Jason Xing
2024-04-16 7:42 ` [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper Jason Xing
2024-04-16 7:42 ` [PATCH net-next 2/3] net: rps: protect filter locklessly Jason Xing
@ 2024-04-16 7:42 ` Jason Xing
2 siblings, 0 replies; 5+ messages in thread
From: Jason Xing @ 2024-04-16 7:42 UTC (permalink / raw)
To: edumazet, kuba, pabeni, davem, horms; +Cc: netdev, kerneljasonxing, Jason Xing
From: Jason Xing <kernelxing@tencent.com>
This is the last member in struct rps_dev_flow which should be
protected locklessly. So finish it.
Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
net/core/dev.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 6892682f9cbf..6003553c05fc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4533,7 +4533,7 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
rps_input_queue_tail_save(rflow->last_qtail, head);
}
- rflow->cpu = next_cpu;
+ WRITE_ONCE(rflow->cpu, next_cpu);
return rflow;
}
@@ -4597,7 +4597,7 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
* we can look at the local (per receive queue) flow table
*/
rflow = &flow_table->flows[hash & flow_table->mask];
- tcpu = rflow->cpu;
+ tcpu = READ_ONCE(rflow->cpu);
/*
* If the desired CPU (where last recvmsg was done) is
--
2.37.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper
2024-04-16 7:42 ` [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper Jason Xing
@ 2024-04-17 0:26 ` Jason Xing
0 siblings, 0 replies; 5+ messages in thread
From: Jason Xing @ 2024-04-17 0:26 UTC (permalink / raw)
To: edumazet, kuba, pabeni, davem, horms; +Cc: netdev, Jason Xing
On Tue, Apr 16, 2024 at 3:42 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> From: Jason Xing <kernelxing@tencent.com>
>
> Only one left place should be proctected locklessly. This patch made it.
>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
> net/core/dev.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 854a3a28a8d8..cd97eeae8218 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);
I made a mistake. I should pass &rflow->last_qtail actually. Will update it.
> }
>
> rflow->cpu = next_cpu;
> --
> 2.37.3
>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-04-17 0:26 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2024-04-16 7:42 [PATCH net-next 0/3] locklessly protect left members in struct rps_dev_flow Jason Xing
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2024-04-17 0:26 ` Jason Xing
2024-04-16 7:42 ` [PATCH net-next 2/3] net: rps: protect filter locklessly Jason Xing
2024-04-16 7:42 ` [PATCH net-next 3/3] net: rps: locklessly access rflow->cpu Jason Xing
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