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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 <bigeasy@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Waiman Long <longman@redhat.com> Link: https://lkml.kernel.org/r/YgKjciR60fZft2l4@linutronix.de
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1 changed files with 3 additions and 3 deletions
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@ -44,9 +44,9 @@ static inline void local_lock_debug_init(local_lock_t *l)
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}
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#else /* CONFIG_DEBUG_LOCK_ALLOC */
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# define LOCAL_LOCK_DEBUG_INIT(lockname)
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static inline void local_lock_acquire(local_lock_t *l) { }
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static inline void local_lock_release(local_lock_t *l) { }
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static inline void local_lock_debug_init(local_lock_t *l) { }
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# define local_lock_acquire(__ll) do { typecheck(local_lock_t *, __ll); } while (0)
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# define local_lock_release(__ll) do { typecheck(local_lock_t *, __ll); } while (0)
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# define local_lock_debug_init(__ll) do { typecheck(local_lock_t *, __ll); } while (0)
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#endif /* !CONFIG_DEBUG_LOCK_ALLOC */
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#define INIT_LOCAL_LOCK(lockname) { LOCAL_LOCK_DEBUG_INIT(lockname) }
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