From: Uros Bizjak <ubizjak@gmail.com>
Date: Fri, 19 Jul 2024 10:38:52 +0000 (+0200)
Subject: kexec: use atomic_try_cmpxchg_acquire() in kexec_trylock()
X-Git-Tag: v6.12-rc1~114^2~98
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=acf02be3c72f12c31f916d3465c4c716b4729538;p=thirdparty%2Fkernel%2Flinux.git

kexec: use atomic_try_cmpxchg_acquire() in kexec_trylock()

Use atomic_try_cmpxchg_acquire(*ptr, &old, new) instead of
atomic_cmpxchg_acquire(*ptr, old, new) == old in kexec_trylock().
x86 CMPXCHG instruction returns success in ZF flag, so
this change saves a compare after cmpxchg.

Link: https://lkml.kernel.org/r/20240719103937.53742-1-ubizjak@gmail.com
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h
index 2595defe8c0d9..d35d9792402d1 100644
--- a/kernel/kexec_internal.h
+++ b/kernel/kexec_internal.h
@@ -23,7 +23,8 @@ int kimage_is_destination_range(struct kimage *image,
 extern atomic_t __kexec_lock;
 static inline bool kexec_trylock(void)
 {
-	return atomic_cmpxchg_acquire(&__kexec_lock, 0, 1) == 0;
+	int old = 0;
+	return atomic_try_cmpxchg_acquire(&__kexec_lock, &old, 1);
 }
 static inline void kexec_unlock(void)
 {