The patch titled
Subject: kexec: use atomic_try_cmpxchg_acquire() in kexec_trylock()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
kexec-use-atomic_try_cmpxchg_acquire-in-kexec_trylock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-use-atomic_try_cmpxchg_acquire-in-kexec_trylock.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Uros Bizjak <ubizjak@xxxxxxxxx>
Subject: kexec: use atomic_try_cmpxchg_acquire() in kexec_trylock()
Date: Fri, 19 Jul 2024 12:38:52 +0200
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@xxxxxxxxx
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Acked-by: Baoquan He <bhe@xxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kexec_internal.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/kexec_internal.h~kexec-use-atomic_try_cmpxchg_acquire-in-kexec_trylock
+++ a/kernel/kexec_internal.h
@@ -23,7 +23,8 @@ int kimage_is_destination_range(struct k
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)
{
_
Patches currently in -mm which might be from ubizjak@xxxxxxxxx are
kexec-use-atomic_try_cmpxchg_acquire-in-kexec_trylock.patch
