Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1246123

Re: [PATCH] mutex: make mutex_lock_nested an inline function

Show all headers | View raw

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.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-13 22:40 +0200
  Re: [PATCH] mutex: make mutex_lock_nested an inline function Arnd Bergmann <arnd@arndb.de> - 2015-10-13 23:50 +0200
    Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-14 10:30 +0200
      Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-14 10:40 +0200
        Re: [PATCH] mutex: make mutex_lock_nested an inline function Arnd Bergmann <arnd@arndb.de> - 2015-10-14 11:10 +0200
          Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-14 11:10 +0200
            Re: [PATCH] mutex: make mutex_lock_nested an inline function Mark Brown <broonie@kernel.org> - 2015-10-14 12:10 +0200
      Re: [PATCH] mutex: make mutex_lock_nested an inline function Mark Brown <broonie@kernel.org> - 2015-10-14 12:30 +0200
        Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-14 13:10 +0200
          Re: [PATCH] mutex: make mutex_lock_nested an inline function Mark Brown <broonie@kernel.org> - 2015-10-14 14:40 +0200
            Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-14 15:50 +0200
              Re: [PATCH] mutex: make mutex_lock_nested an inline function Peter Zijlstra <peterz@infradead.org> - 2015-10-14 16:00 +0200
                Re: [PATCH] mutex: make mutex_lock_nested an inline function Ingo Molnar <mingo@kernel.org> - 2015-10-14 16:00 +0200
              Re: [PATCH] mutex: make mutex_lock_nested an inline function Mark Brown <broonie@kernel.org> - 2015-10-14 16:20 +0200

csiph-web