* [PATCH] sched/rt: Use atomic_try_cmpxchg_acquire() in rto_start_trylock()
@ 2026-04-15 12:40 David Carlier
2026-04-15 18:14 ` Uros Bizjak
0 siblings, 1 reply; 2+ messages in thread
From: David Carlier @ 2026-04-15 12:40 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Valentin Schneider, K Prateek Nayak
Cc: David Carlier, linux-kernel
Replace this pattern in rto_start_trylock():
!atomic_cmpxchg_acquire(*ptr, 0, new)
... with the simpler and faster:
atomic_try_cmpxchg_acquire(*ptr, &zero, new)
The x86 CMPXCHG instruction returns success in the ZF flag, so
atomic_try_cmpxchg_acquire() saves a compare after the CMPXCHG.
No functional change intended.
Signed-off-by: David Carlier <devnexen@gmail.com>
---
kernel/sched/rt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 4ee8faf01441..13ac94899c18 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2172,7 +2172,8 @@ static int rto_next_cpu(struct root_domain *rd)
static inline bool rto_start_trylock(atomic_t *v)
{
- return !atomic_cmpxchg_acquire(v, 0, 1);
+ int zero = 0;
+ return atomic_try_cmpxchg_acquire(v, &zero, 1);
}
static inline void rto_start_unlock(atomic_t *v)
--
2.53.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] sched/rt: Use atomic_try_cmpxchg_acquire() in rto_start_trylock()
2026-04-15 12:40 [PATCH] sched/rt: Use atomic_try_cmpxchg_acquire() in rto_start_trylock() David Carlier
@ 2026-04-15 18:14 ` Uros Bizjak
0 siblings, 0 replies; 2+ messages in thread
From: Uros Bizjak @ 2026-04-15 18:14 UTC (permalink / raw)
To: David Carlier, Ingo Molnar, Peter Zijlstra, Juri Lelli,
Vincent Guittot, Dietmar Eggemann, Steven Rostedt, Ben Segall,
Mel Gorman, Valentin Schneider, K Prateek Nayak
Cc: linux-kernel
On 4/15/26 14:40, David Carlier wrote:
> Replace this pattern in rto_start_trylock():
>
> !atomic_cmpxchg_acquire(*ptr, 0, new)
>
> ... with the simpler and faster:
>
> atomic_try_cmpxchg_acquire(*ptr, &zero, new)
>
> The x86 CMPXCHG instruction returns success in the ZF flag, so
> atomic_try_cmpxchg_acquire() saves a compare after the CMPXCHG.
>
> No functional change intended.
>
> Signed-off-by: David Carlier <devnexen@gmail.com>
Reviewed-by: Uros Bizjak <ubizjak@gmail.com>
> ---
> kernel/sched/rt.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 4ee8faf01441..13ac94899c18 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -2172,7 +2172,8 @@ static int rto_next_cpu(struct root_domain *rd)
>
> static inline bool rto_start_trylock(atomic_t *v)
> {
> - return !atomic_cmpxchg_acquire(v, 0, 1);
> + int zero = 0;
> + return atomic_try_cmpxchg_acquire(v, &zero, 1);
> }
>
> static inline void rto_start_unlock(atomic_t *v)
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-04-15 18:14 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-04-15 12:40 [PATCH] sched/rt: Use atomic_try_cmpxchg_acquire() in rto_start_trylock() David Carlier
2026-04-15 18:14 ` Uros Bizjak
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox