linux-kernel - Re: [PATCH RESEND] spin_lock_*(): Always evaluate second argument

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Message-Id: <20140722133716.cff957eff4eff1cc9c1d9968@linux-foundation.org>
Date:	Tue, 22 Jul 2014 13:37:16 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Bart Van Assche <bvanassche@....org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND] spin_lock_*(): Always evaluate second argument

On Tue, 22 Jul 2014 09:17:45 +0200 Bart Van Assche <bvanassche@....org> wrote:

> Evaluating a macro argument only if certain configuration options
> have been selected is confusing and error-prone. Hence always
> evaluate the second argument of spin_lock_nested() and
> spin_lock_nest_lock().
> 
> An intentional side effect of this patch is that it avoids that
> the following warning is reported for netif_addr_lock_nested()
> when building with CONFIG_DEBUG_LOCK_ALLOC=n and with W=1:
> 
> ...
>
> --- a/include/linux/spinlock.h
> +++ b/include/linux/spinlock.h
> @@ -197,8 +197,10 @@ static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
>  		 _raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map);	\
>  	 } while (0)
>  #else
> -# define raw_spin_lock_nested(lock, subclass)		_raw_spin_lock(lock)
> -# define raw_spin_lock_nest_lock(lock, nest_lock)	_raw_spin_lock(lock)
> +# define raw_spin_lock_nested(lock, subclass)		\
> +	((void)(subclass), _raw_spin_lock(lock))
> +# define raw_spin_lock_nest_lock(lock, nest_lock)	\
> +	((void)(nest_lock), _raw_spin_lock(lock))
>  #endif
>  

Did you try converting these to static inline functions?  That should
squish the warning and makes the code nicer instead of nastier...

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