linux-kernel - Re: [PATCH v1] sched/topology: Make compiler happy about unused constant definitions

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Message-ID: <20200825082636.GQ1891694@smile.fi.intel.com>
Date:   Tue, 25 Aug 2020 11:26:36 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-kernel@...r.kernel.org,
        Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v1] sched/topology: Make compiler happy about unused
 constant definitions

On Mon, Aug 24, 2020 at 06:09:41PM +0100, Valentin Schneider wrote:
> On 24/08/20 16:39, Andy Shevchenko wrote:
> > Compilation of almost each file ends up with
> >
> >  In file included from .../include/linux/energy_model.h:10,
> >                 from .../include/linux/device.h:16,
> >                 from .../drivers/spi/spi.c:8:
> >  .../include/linux/sched/topology.h:30:27: warning: ‘SD_DEGENERATE_GROUPS_MASK’ defined but not used [-Wunused-const-variable=]
> >     30 | static const unsigned int SD_DEGENERATE_GROUPS_MASK =
> >        |                           ^~~~~~~~~~~~~~~~~~~~~~~~~
> >  ...
> >
> > Make compiler happy by annotating the static constants with __maybwe_unused.
> >
> 
> That should see some use as long as the build is for SMP. This whole region
> is guarded by #ifdef CONFIG_SMP, so an !SMP build shouldn't trigger this.

Isn't SMP is default for most of the kernel builds?
And honestly I didn't get the purpose of this comment.

> With what config/kernel are you getting this?

x86_64_defconfig from the kernel sources with some drivers added (SMP or so has
not been touched, DEBUG_SHED was enabled once to confirm that another static
const has same issue).

-- 
With Best Regards,
Andy Shevchenko