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.
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
---
kernel/kexec_core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index be5642a4ec49..bc4c096ab1f3 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);
--
2.41.0
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