From 8491d1bdf5de152f27fc941e2dcdc4e66c950542 Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Wed, 18 May 2022 20:49:53 +0200 Subject: [PATCH] sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote} Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in sched_clock_{local,remote}. x86 cmpxchg returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Signed-off-by: Uros Bizjak Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20220518184953.3446778-1-ubizjak@gmail.com --- kernel/sched/clock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index d9272d9..e374c0c 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -287,7 +287,7 @@ again: clock = wrap_max(clock, min_clock); clock = wrap_min(clock, max_clock); - if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock) + if (!try_cmpxchg64(&scd->clock, &old_clock, clock)) goto again; return clock; @@ -349,7 +349,7 @@ again: val = remote_clock; } - if (cmpxchg64(ptr, old_val, val) != old_val) + if (!try_cmpxchg64(ptr, &old_val, val)) goto again; return val; -- 2.7.4