locking/local_lock: Make the empty local_lock_*() function a macro.
authorSebastian Andrzej Siewior <bigeasy@linutronix.de>
Tue, 8 Feb 2022 17:08:02 +0000 (18:08 +0100)
committerPeter Zijlstra <peterz@infradead.org>
Fri, 11 Feb 2022 11:13:56 +0000 (12:13 +0100)
commit9983a9d577db415c41099a20a5637ab25dd3c240
treed45ce6b145ecfbdda34fe388e1f17e26db3e4bbb
parentdc1b4df09acdca7a89806b28f235cd6d8dcd3d24
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
include/linux/local_lock_internal.h