sched/fair: use try_cmpxchg in task_numa_work

Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
task_numa_work.  x86 CMPXCHG instruction returns success in ZF flag, so
this change saves a compare after cmpxchg (and related move instruction in
front of cmpxchg).

No functional change intended.

Link: https://lkml.kernel.org/r/20220822173956.82525-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e4a0b8bd941c78446353d275d4b22e283acd21f9..d6fa06f036e12d5f1bedc429c675cbd97275c4d5 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2964,7 +2964,7 @@ static void task_numa_work(struct callback_head *work)
        }
 
        next_scan = now + msecs_to_jiffies(p->numa_scan_period);
-       if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
+       if (!try_cmpxchg(&mm->numa_next_scan, &migrate, next_scan))
                return;
 
        /*