Messages in this thread | | | Date | Tue, 13 Oct 2015 22:38:12 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] mutex: make mutex_lock_nested an inline function |
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On Tue, Oct 13, 2015 at 10:30:08PM +0200, Arnd Bergmann wrote: > The second argument of the mutex_lock_nested() helper is only > evaluated if CONFIG_DEBUG_LOCK_ALLOC is set. Otherwise we > get this build warning for the new regulator_lock_supply > function: > > drivers/regulator/core.c: In function 'regulator_lock_supply': > drivers/regulator/core.c:142:6: warning: unused variable 'i' [-Wunused-variable] > > To avoid the warning, this patch changes the definition of > mutex_lock_nested() to be static inline function rather than > a macro, which tells gcc that the variable is potentially > used.
> -# define mutex_lock_nested(lock, subclass) mutex_lock(lock) > +static inline void mutex_lock_nested(struct mutex *lock, unsigned int subclass) > +{ > + return mutex_lock(lock); > +}
Can you verify that this results in an identical kernel?
Having this a proper argument results in the compiler having to actually evaluate the expression resulting in @subclass, this might have side effects and generate code.
A quick grep shows a large amount of trivial code that optimizers will still happily throw away, but it should be verified that this does not result in pointless code generation.
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