diff mbox series

[net-next,v3,1/3] net: sched: avoid unnecessary seqcount operation for lockless qdisc

Message ID 1624344597-11806-2-git-send-email-linyunsheng@huawei.com (mailing list archive)
State Accepted
Commit dd25296afaf60b5140ddfa9e3d8e5d9df7076754
Delegated to: Netdev Maintainers
Headers show
Series Some optimization for lockless qdisc | expand

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netdev/tree_selection success Clearly marked for net-next
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netdev/cc_maintainers success CCed 12 of 12 maintainers
netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 3423 this patch: 3423
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success Link
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 22 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 3519 this patch: 3519
netdev/header_inline success Link

Commit Message

Yunsheng Lin June 22, 2021, 6:49 a.m. UTC 
qdisc->running seqcount operation is mainly used to do heuristic
locking on q->busylock for locked qdisc, see qdisc_is_running()
and __dev_xmit_skb().

So avoid doing seqcount operation for qdisc with TCQ_F_NOLOCK
flag.

Acked-by: Jakub Kicinski <kuba@kernel.org>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com> # flexcan
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
---
 include/net/sch_generic.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 1e62551..3ed6bcc 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -188,6 +188,7 @@  static inline bool qdisc_run_begin(struct Qdisc *qdisc)
 
 nolock_empty:
 		WRITE_ONCE(qdisc->empty, false);
+		return true;
 	} else if (qdisc_is_running(qdisc)) {
 		return false;
 	}
@@ -201,7 +202,6 @@  static inline bool qdisc_run_begin(struct Qdisc *qdisc)
 
 static inline void qdisc_run_end(struct Qdisc *qdisc)
 {
-	write_seqcount_end(&qdisc->running);
 	if (qdisc->flags & TCQ_F_NOLOCK) {
 		spin_unlock(&qdisc->seqlock);
 
@@ -210,6 +210,8 @@  static inline void qdisc_run_end(struct Qdisc *qdisc)
 			clear_bit(__QDISC_STATE_MISSED, &qdisc->state);
 			__netif_schedule(qdisc);
 		}
+	} else {
+		write_seqcount_end(&qdisc->running);
 	}
 }