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sched/clock: Use try_cmpxchg64 in sched_clock_{local,remote}

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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 <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220518184953.3446778-1-ubizjak@gmail.com
This commit is contained in:
Uros Bizjak
2022-05-18 20:49:53 +02:00
committed by Peter Zijlstra
parent c2df0a6af1
commit 8491d1bdf5
1 changed files with 2 additions and 2 deletions
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4
kernel/sched/clock.c
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@@ -287,7 +287,7 @@ again:
clock = wrap_max(clock, min_clock); clock = wrap_max(clock, min_clock);
clock = wrap_min(clock, max_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; goto again;
return clock; return clock;
@@ -349,7 +349,7 @@ again:
val = remote_clock; val = remote_clock;
} }
if (cmpxchg64(ptr, old_val, val) != old_val) if (!try_cmpxchg64(ptr, &old_val, val))
goto again; goto again;
return val; return val;