[PATCH v1] sched/topology: Make compiler happy about unused constant definitions

[PATCH v1] sched/topology: Make compiler happy about unused constant definitions

[Andy Shevchenko]

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.

Fixes: 4ee4ea443a5d ("sched/topology: Introduce SD metaflag for flags needing > 1 groups")
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 include/linux/sched/topology.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index 2d59ca77103e..ec440b67599c 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -27,14 +27,14 @@ 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 =
+static __maybe_unused const unsigned int SD_DEGENERATE_GROUPS_MASK =
 #include <linux/sched/sd_flags.h>
 0;
 #undef SD_FLAG
 
 #ifdef CONFIG_SCHED_DEBUG
 #define SD_FLAG(_name, mflags) [__##_name] = { .meta_flags = mflags, .name = #_name },
-static const struct {
+static __maybe_unused const struct {
 	unsigned int meta_flags;
 	char *name;
 } sd_flag_debug[] = {
-- 
2.28.0

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

[Valentin Schneider]

Hi,

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.

With what config/kernel are you getting this?

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

[Andy Shevchenko]

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

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

[Valentin Schneider]

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.
>> >
>>
>> 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.
>

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.

>> 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).

Thanks, I'll poke around this.

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

[Valentin Schneider]

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

RE: [PATCH v1] sched/topology: Make compiler happy about unused constant definitions

[David Laight]

From: Andy Shevchenko
> Sent: 25 August 2020 09:27
> 
> 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.

The real fix is to not use 'static const' in C.
IIRC it is still a memory location (that can be patched) not
a compile time constant.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

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

[Andy Shevchenko]

On Tue, Aug 25, 2020 at 11:12:21AM +0100, Valentin Schneider wrote:
> 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?

% gcc --version
gcc (Debian 10.2.0-5) 10.2.0

% make O=... W=1 C=1 CF=-D__CHECK_ENDIAN__ -j64

> Alternatively we can make this a "proper" constant expression with the
> below.

It doesn't fix another static const in the same file, though that one requires
DEBUG_SCHED to be enabled.

Do you want me to split this fix and fix only the other case?

> ---
> 
> 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

-- 
With Best Regards,
Andy Shevchenko

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

[Andy Shevchenko]

On Tue, Aug 25, 2020 at 02:24:05PM +0300, Andy Shevchenko wrote:
> On Tue, Aug 25, 2020 at 11:12:21AM +0100, Valentin Schneider wrote:
> > 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?
> 
> % gcc --version
> gcc (Debian 10.2.0-5) 10.2.0
> 
> % make O=... W=1 C=1 CF=-D__CHECK_ENDIAN__ -j64
> 
> > Alternatively we can make this a "proper" constant expression with the
> > below.
> 
> It doesn't fix another static const in the same file, though that one requires
> DEBUG_SCHED to be enabled.
> 
> Do you want me to split this fix and fix only the other case?

Just checked and the other case has been brought by

b6e862f38672 ("sched/topology: Define and assign sched_domain flag metadata")

with your authorship.

-- 
With Best Regards,
Andy Shevchenko

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

['Andy Shevchenko']

On Tue, Aug 25, 2020 at 10:23:05AM +0000, David Laight wrote:
> From: Andy Shevchenko
> > Sent: 25 August 2020 09:27
> > 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.
> 
> The real fix is to not use 'static const' in C.
> IIRC it is still a memory location (that can be patched) not
> a compile time constant.

Yep. The topology.h can be rather split to topology.c with exported symbols
(exported or just visible for linker, depends on the case).

-- 
With Best Regards,
Andy Shevchenko

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

[Andy Shevchenko]

On Tue, Aug 25, 2020 at 02:26:05PM +0300, Andy Shevchenko wrote:
> On Tue, Aug 25, 2020 at 02:24:05PM +0300, Andy Shevchenko wrote:
> > On Tue, Aug 25, 2020 at 11:12:21AM +0100, Valentin Schneider wrote:
> > > 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.

And even without compiler or any other analyzer / bot I can 100% sure tell that
spi.c does *not* use that symbol.

-- 
With Best Regards,
Andy Shevchenko

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

[Valentin Schneider]

On 25/08/20 12:32, Andy Shevchenko wrote:
> On Tue, Aug 25, 2020 at 02:26:05PM +0300, Andy Shevchenko wrote:
>> On Tue, Aug 25, 2020 at 02:24:05PM +0300, Andy Shevchenko wrote:
>> > On Tue, Aug 25, 2020 at 11:12:21AM +0100, Valentin Schneider wrote:
>> > > 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.
>
> And even without compiler or any other analyzer / bot I can 100% sure tell that
> spi.c does *not* use that symbol.

Aye aye, this is a daft constvar placement from my end, apologies.

For the SD_DEGENERATE_GROUPS_MASK, that one could directly be shoved into
kernel/sched/topology.c (or done via an enum, I don't care too much).

I suppose the other one causing you grief is sd_flag_debug[]; that one too
really shouldn't be in a header. I need to access that in two separate
files, so I guess I'll have to cook up some wrappers.

Let me take a jab at it, it's my own mess after all...

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

[Andy Shevchenko]

On Tue, Aug 25, 2020 at 01:00:12PM +0100, Valentin Schneider wrote:
> On 25/08/20 12:32, Andy Shevchenko wrote:
> > On Tue, Aug 25, 2020 at 02:26:05PM +0300, Andy Shevchenko wrote:
> >> On Tue, Aug 25, 2020 at 02:24:05PM +0300, Andy Shevchenko wrote:
> >> > On Tue, Aug 25, 2020 at 11:12:21AM +0100, Valentin Schneider wrote:
> >> > > 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.
> >
> > And even without compiler or any other analyzer / bot I can 100% sure tell that
> > spi.c does *not* use that symbol.
> 
> Aye aye, this is a daft constvar placement from my end, apologies.
> 
> For the SD_DEGENERATE_GROUPS_MASK, that one could directly be shoved into
> kernel/sched/topology.c (or done via an enum, I don't care too much).
> 
> I suppose the other one causing you grief is sd_flag_debug[]; that one too
> really shouldn't be in a header. I need to access that in two separate
> files, so I guess I'll have to cook up some wrappers.
> 
> Let me take a jab at it, it's my own mess after all...

Thank you!
Ping me if you would need to test a patch or so.

-- 
With Best Regards,
Andy Shevchenko