From: Uros Bizjak Date: Tue, 14 Nov 2023 16:12:01 +0000 (+0100) Subject: kexec: use atomic_try_cmpxchg in crash_kexec X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0311d8272406b2ec47f485bef887723cc352a489;p=linux.git kexec: use atomic_try_cmpxchg in crash_kexec Use atomic_try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in crash_kexec(). x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg. No functional change intended. Link: https://lkml.kernel.org/r/20231114161228.108516-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak Acked-by: Baoquan He Cc: Eric Biederman Signed-off-by: Andrew Morton --- diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index be5642a4ec490..bc4c096ab1f3e 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1063,9 +1063,10 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs) * panic(). Otherwise parallel calls of panic() and crash_kexec() * may stop each other. To exclude them, we use panic_cpu here too. */ + old_cpu = PANIC_CPU_INVALID; this_cpu = raw_smp_processor_id(); - old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu); - if (old_cpu == PANIC_CPU_INVALID) { + + if (atomic_try_cmpxchg(&panic_cpu, &old_cpu, this_cpu)) { /* This is the 1st CPU which comes here, so go ahead. */ __crash_kexec(regs);