perf/x86: Use local64_try_cmpxchg
authorUros Bizjak <ubizjak@gmail.com>
Thu, 6 Jul 2023 14:16:48 +0000 (16:16 +0200)
committerPeter Zijlstra <peterz@infradead.org>
Mon, 10 Jul 2023 07:52:35 +0000 (09:52 +0200)
commit4c1c9dea2089374cb58505a0df6136969ff3c8b9
tree31ccb01e981ee0bf63342378bbd0f1e3c2ff3474
parent7c2128235eff99b448af8f4b5b2933495bf1a440
perf/x86: Use local64_try_cmpxchg

Use local64_try_cmpxchg instead of local64_cmpxchg (*ptr, old, new) == old.
x86 CMPXCHG instruction returns success in ZF flag, so this change saves a
compare after cmpxchg (and related move instruction in front of cmpxchg).

Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
fails. There is no need to re-read the value in the loop.

No functional change intended.

Cc. "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230706141720.2672-1-ubizjak@gmail.com
arch/x86/events/amd/ibs.c
arch/x86/events/core.c
arch/x86/events/intel/cstate.c
arch/x86/events/msr.c