diff mbox series

[net-next,v3,1/3] net: rps: protect last_qtail with rps_input_queue_tail_save() helper

Message ID 20240418073603.99336-2-kerneljasonxing@gmail.com (mailing list archive)
State Accepted
Commit 84b6823cd96b38c40b3b30beabbfa48d92990e1a
Delegated to: Netdev Maintainers
Headers show
Series locklessly protect left members in struct rps_dev_flow | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 933 this patch: 933
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 4 of 4 maintainers
netdev/build_clang success Errors and warnings before: 938 this patch: 938
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 944 this patch: 944
netdev/checkpatch warning WARNING: line length of 83 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 79 this patch: 79
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-04-19--00-00 (tests: 961)

Commit Message

Jason Xing April 18, 2024, 7:36 a.m. UTC 
From: Jason Xing <kernelxing@tencent.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@tencent.com>
---
 net/core/dev.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Eric Dumazet April 19, 2024, 5:57 a.m. UTC | #1 
On Thu, Apr 18, 2024 at 9:36 AM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> From: Jason Xing <kernelxing@tencent.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@tencent.com>

Reviewed-by: Eric Dumazet <edumazet@google.com>
John Sperbeck May 29, 2024, 8:34 p.m. UTC | #2 
If CONFIG_RFS_ACCEL is off, then I think there will be a compile error with this change, since 'head' is used, but no longer defined.
Eric Dumazet May 29, 2024, 8:45 p.m. UTC | #3 
On Wed, May 29, 2024 at 10:34 PM John Sperbeck <jsperbeck@google.com> wrote:
>
> If CONFIG_RFS_ACCEL is off, then I think there will be a compile error with this change, since 'head' is used, but no longer defined.

I assume you are speaking of this commit ?

commit 84b6823cd96b38c40b3b30beabbfa48d92990e1a
Author: Jason Xing <kernelxing@tencent.com>
Date:   Thu Apr 18 15:36:01 2024 +0800

    net: rps: protect last_qtail with rps_input_queue_tail_save() helper
Jason Xing May 30, 2024, 2:55 a.m. UTC | #4 
Hi John,

On Thu, May 30, 2024 at 4:34 AM John Sperbeck <jsperbeck@google.com> wrote:
>
> If CONFIG_RFS_ACCEL is off, then I think there will be a compile error with this change, since 'head' is used, but no longer defined.

Thanks for your report. I'll fix it today.
Jason Xing May 30, 2024, 2:56 a.m. UTC | #5 
On Thu, May 30, 2024 at 4:45 AM Eric Dumazet <edumazet@google.com> wrote:
>
> On Wed, May 29, 2024 at 10:34 PM John Sperbeck <jsperbeck@google.com> wrote:
> >
> > If CONFIG_RFS_ACCEL is off, then I think there will be a compile error with this change, since 'head' is used, but no longer defined.
>
> I assume you are speaking of this commit ?
>
> commit 84b6823cd96b38c40b3b30beabbfa48d92990e1a
> Author: Jason Xing <kernelxing@tencent.com>
> Date:   Thu Apr 18 15:36:01 2024 +0800
>
>     net: rps: protect last_qtail with rps_input_queue_tail_save() helper

Yes, I will fix it soon.

Thanks,
Jason
diff mbox series

Patch

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);
 		}