diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2023-08-30 17:13:57 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2023-09-15 13:19:22 +0200 |
| commit | b8e3dfa16ec55f310dd95831614af3d24abf5ed5 (patch) | |
| tree | 61d423ee6dddb280e6db7558c9804d9f6de2c230 /arch/x86/include/asm/preempt.h | |
| parent | 5f863897d964e834a0da35b1e483b5bb8faca522 (diff) | |
x86/percpu: Use raw_cpu_try_cmpxchg() in preempt_count_set()
Use raw_cpu_try_cmpxchg() instead of raw_cpu_cmpxchg(*ptr, old, new) == old.
x86 CMPXCHG instruction returns success in ZF flag, so this change saves a
compare after CMPXCHG (and related MOV instruction in front of CMPXCHG).
Also, raw_cpu_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.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230830151623.3900-2-ubizjak@gmail.com
Diffstat (limited to 'arch/x86/include/asm/preempt.h')
| -rw-r--r-- | arch/x86/include/asm/preempt.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index 2d13f25b1bd8..4527e1430c6d 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -31,11 +31,11 @@ static __always_inline void preempt_count_set(int pc) { int old, new; + old = raw_cpu_read_4(pcpu_hot.preempt_count); do { - old = raw_cpu_read_4(pcpu_hot.preempt_count); new = (old & PREEMPT_NEED_RESCHED) | (pc & ~PREEMPT_NEED_RESCHED); - } while (raw_cpu_cmpxchg_4(pcpu_hot.preempt_count, old, new) != old); + } while (!raw_cpu_try_cmpxchg_4(pcpu_hot.preempt_count, &old, new)); } /* |