linux-kernel - Re: locking/local_lock, mm: sparse warnings about shadowed variable

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Message-Id: <20250611153347.779ae8c66be1aa806dbeb816@linux-foundation.org>
Date: Wed, 11 Jun 2025 15:33:47 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Vlastimil Babka <vbabka@...e.cz>, Charlemagne Lasse
 <charlemagnelasse@...il.com>, Johannes Weiner <hannes@...xchg.org>, Michal
 Hocko <mhocko@...nel.org>, Roman Gushchin <roman.gushchin@...ux.dev>,
 Shakeel Butt <shakeel.butt@...ux.dev>, Muchun Song <muchun.song@...ux.dev>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>, Clark Williams
 <clrkwllms@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, Alexei
 Starovoitov <ast@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Jakub
 Kicinski <kuba@...nel.org>, "Peter Zijlstra (Intel)"
 <peterz@...radead.org>, Davidlohr Bueso <dave@...olabs.net>, LKML
 <linux-kernel@...r.kernel.org>, "open list:CONTROL GROUP (CGROUP)"
 <cgroups@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
 linux-rt-devel@...ts.linux.dev
Subject: Re: locking/local_lock, mm: sparse warnings about shadowed variable

On Wed, 11 Jun 2025 11:20:16 -0700 Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> > diff --git a/include/linux/local_lock_internal.h b/include/linux/local_lock_internal.h
> > index 8d5ac16a9b17..075338f270d0 100644
> > --- a/include/linux/local_lock_internal.h
> > +++ b/include/linux/local_lock_internal.h
> > @@ -97,17 +97,17 @@ do {                                                                \
> >  #define __local_lock_acquire(lock)                                     \
> >         do {                                                            \
> >                 local_trylock_t *tl;                                    \
> > -               local_lock_t *l;                                        \
> > +               local_lock_t *ll;                                       \
> 
> I wouldn't bother messing with the code because of sparse.
> Compilers don't warn here.

There's some value in not cluttering up the sparse output in this
fashion.  sparse does often find things which we choose to fix.