linux-kernel - Re: [PATCH v1 1/1] sched: Remove never used code in mm_cid

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Message-ID: <20251024211901.GC2068@quark>
Date: Fri, 24 Oct 2025 14:19:01 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>
Subject: Re: [PATCH v1 1/1] sched: Remove never used code in mm_cid_get()

On Mon, Oct 20, 2025 at 12:49:34PM +0200, Peter Zijlstra wrote:
> On Mon, Oct 20, 2025 at 01:10:44PM +0300, Andy Shevchenko wrote:
> > On Wed, Oct 15, 2025 at 11:19:34AM +0200, Andy Shevchenko wrote:
> > > Clang is not happy with set but unused variable (this is visible
> > > with `make W=1` build:
> > > 
> > > kernel/sched/sched.h:3744:18: error: variable 'cpumask' set but not used [-Werror,-Wunused-but-set-variable]
> > > 
> > > It seems like the variable was never be used along with the assignment that
> > > does not have side effects as far as I can see. Remove those altogether.
> > 
> > Anybody to apply this for fixes?
> 
> Why? W=1 and WERROR is very much you get to keep the pieces land, no?

Tested-by: Eric Biggers <ebiggers@...nel.org>

Linus, could you consider applying this directly?  This seems to have
broken W=1 for basically the whole kernel.  I see many other people
already ran into this and sent the same patch
(https://lore.kernel.org/r/20251002-sched-w1-v1-1-a6fdf549d179@linaro.org
https://lore.kernel.org/r/20251009194818.1587650-1-kriish.sharma2006@gmail.com
https://lore.kernel.org/r/20251017073050.2411988-1-kevin.brodsky@arm.com
https://lore.kernel.org/r/20251020220601.176639-1-adigollamudi@gmail.com)
but unfortunately the maintainer is refusing to apply any of them.

I find W=1 to be useful, and I keep my subsystems W=1 clean.  But I
cannot do that if W=1 is broken for all kernel builds.

I think it's clear that a lot of other people find it useful too.

- Eric