linux-kernel - Re: [PATCH v3] locking/local_lock: s/l/__l/ and s/tl/_

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Message-ID: <20251009124315.KS20u0OG@linutronix.de>
Date: Thu, 9 Oct 2025 14:43:15 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Vincent Mailhol <mailhol@...nel.org>
Cc: linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v3] locking/local_lock: s/l/__l/ and s/tl/__tl/ to reduce
 risk of shadowing

On 2025-10-09 21:39:07 [+0900], Vincent Mailhol wrote:
> Hi Sebastian,
Hi Vincent,

> On 09/10/2025 at 19:39, Sebastian Andrzej Siewior wrote:
> 
> (...)
> 
> > @@ -223,12 +223,12 @@ typedef spinlock_t local_trylock_t;
> >  #define INIT_LOCAL_LOCK(lockname) __LOCAL_SPIN_LOCK_UNLOCKED((lockname))
> >  #define INIT_LOCAL_TRYLOCK(lockname) __LOCAL_SPIN_LOCK_UNLOCKED((lockname))
> >  
> > -#define __local_lock_init(l)					\
> > +#define __local_lock_init(__l)					\
> >  	do {							\
> > -		local_spin_lock_init((l));			\
> > +		local_spin_lock_init((__l));			\
> >  	} while (0)
> >  
> > -#define __local_trylock_init(l)			__local_lock_init(l)
> > +#define __local_trylock_init(__l)			__local_lock_init(__l)
> >  
> >  #define __local_lock(__lock)					\
> >  	do {							\
> 
> The parameters of a function like macro can not shadow existing
> symbols because, when invoked, these parameters would be substituted
> during the macro expansion by the actual arguments. Only the local
> variables declared in the macro would survive after the preprocessor
> and thus only those may cause shadowing.
> 
> So this last part of the patch is not needed.

Right, but then we have the same __l variable in the whole file. Isn't
this worth something?

> Yours sincerely,
> Vincent Mailhol

Sebastian