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Date: Tue, 25 Aug 2020 11:12:21 +0100 From: Valentin Schneider <valentin.schneider@....com> To: Andy Shevchenko <andriy.shevchenko@...ux.intel.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 25/08/20 10:03, Valentin Schneider wrote: > On 25/08/20 09:26, Andy Shevchenko wrote: >> 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. > Sorry, that's what I get for trying to be too succinct; what I tried to say > was that SD_DEGENERATE_GROUPS_MASK should very much be used for SMP. If the > build is !SMP, it shouldn't even be defined, IOW I'm perplexed as to where > this is coming from. So I see how having this as a constvar rather than a constexpr is somewhat daft (we get an instance per compilation unit), but none of my compilers seem to complain (even with W=1). AFAIA the kernelbot didn't catch any of it either. Out of curiosity, what's your compiler & compiler version? Alternatively we can make this a "proper" constant expression with the below. --- diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 2d59ca77103e..b1331c4c48e9 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -27,9 +27,11 @@ enum { /* Generate a mask of SD flags with the SDF_NEEDS_GROUPS metaflag */ #define SD_FLAG(name, mflags) (name * !!((mflags) & SDF_NEEDS_GROUPS)) | -static const unsigned int SD_DEGENERATE_GROUPS_MASK = +enum { + SD_DEGENERATE_GROUPS_MASK = #include <linux/sched/sd_flags.h> -0; +0 +}; #undef SD_FLAG #ifdef CONFIG_SCHED_DEBUG
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