diff mbox series

[RFC,v4,1/3] net: sched: avoid unnecessary seqcount operation for lockless qdisc

Message ID 1621502873-62720-2-git-send-email-linyunsheng@huawei.com (mailing list archive)
State Superseded
Delegated to: Netdev Maintainers
Headers show
Series Some optimization for lockless qdisc | expand

Checks

Context Check Description
netdev/tree_selection success Guessing tree name failed - patch did not apply

Commit Message

Yunsheng Lin May 20, 2021, 9:27 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.

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);
 	}
 }