From 9983a9d577db415c41099a20a5637ab25dd3c240 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 8 Feb 2022 18:08:02 +0100 Subject: [PATCH] locking/local_lock: Make the empty local_lock_*() function a macro. It has been said that local_lock() does not add any overhead compared to preempt_disable() in a !LOCKDEP configuration. A micro benchmark showed an unexpected result which can be reduced to the fact that local_lock() was not entirely optimized away. In the !LOCKDEP configuration local_lock_acquire() is an empty static inline function. On x86 the this_cpu_ptr() argument of that function is fully evaluated leading to an additional mov+add instructions which are not needed and not used. Replace the static inline function with a macro. The typecheck() macro ensures that the argument is of proper type while the resulting disassembly shows no traces of this_cpu_ptr(). Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Waiman Long Link: https://lkml.kernel.org/r/YgKjciR60fZft2l4@linutronix.de --- include/linux/local_lock_internal.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h index 975e33b793a774..6d635e8306d645 100644 --- a/include/linux/local_lock_internal.h +++ b/include/linux/local_lock_internal.h @@ -44,9 +44,9 @@ static inline void local_lock_debug_init(local_lock_t *l) } #else /* CONFIG_DEBUG_LOCK_ALLOC */ # define LOCAL_LOCK_DEBUG_INIT(lockname) -static inline void local_lock_acquire(local_lock_t *l) { } -static inline void local_lock_release(local_lock_t *l) { } -static inline void local_lock_debug_init(local_lock_t *l) { } +# define local_lock_acquire(__ll) do { typecheck(local_lock_t *, __ll); } while (0) +# define local_lock_release(__ll) do { typecheck(local_lock_t *, __ll); } while (0) +# define local_lock_debug_init(__ll) do { typecheck(local_lock_t *, __ll); } while (0) #endif /* !CONFIG_DEBUG_LOCK_ALLOC */ #define INIT_LOCAL_LOCK(lockname) { LOCAL_LOCK_DEBUG_INIT(lockname) }