[PATCH RFC] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[PATCH RFC] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Paul E. McKenney]

The pidfd selftests run in userspace and include both userspace and kernel
header files.  On some distros (for example, CentOS), this results in
duplicate-symbol warnings in allmodconfig builds, while on other distros
(for example, Ubuntu) it does not.  (This happens in recent -next trees,
including next-20250714.)

Therefore, use #undef to get rid of the userspace definitions in favor
of the kernel definitions.

Other ways of handling this include splitting up the selftest code so
that the userspace definitions go into one translation unit and the
kernel definitions into another (which might or might not be feasible)
or to adjust compiler command-line options to suppress the warnings
(which might or might not be desirable).

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <linux-kselftest@vger.kernel.org>

---
 pidfd.h |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
index efd74063126eb..6ff495398e872 100644
--- a/tools/testing/selftests/pidfd/pidfd.h
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -16,6 +16,10 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
+#undef SCHED_NORMAL
+#undef SCHED_FLAG_KEEP_ALL
+#undef SCHED_FLAG_UTIL_CLAMP
+
 #include "../kselftest.h"
 #include "../clone3/clone3_selftests.h"
 

Re: [PATCH RFC] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Shuah Khan]

On 7/14/25 17:01, Paul E. McKenney wrote:
> The pidfd selftests run in userspace and include both userspace and kernel
> header files.  On some distros (for example, CentOS), this results in
> duplicate-symbol warnings in allmodconfig builds, while on other distros
> (for example, Ubuntu) it does not.  (This happens in recent -next trees,
> including next-20250714.)
> 
> Therefore, use #undef to get rid of the userspace definitions in favor
> of the kernel definitions.
> 
> Other ways of handling this include splitting up the selftest code so
> that the userspace definitions go into one translation unit and the
> kernel definitions into another (which might or might not be feasible)
> or to adjust compiler command-line options to suppress the warnings
> (which might or might not be desirable).
> 
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: <linux-kselftest@vger.kernel.org>
> 
> ---
>   pidfd.h |    4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
> index efd74063126eb..6ff495398e872 100644
> --- a/tools/testing/selftests/pidfd/pidfd.h
> +++ b/tools/testing/selftests/pidfd/pidfd.h
> @@ -16,6 +16,10 @@
>   #include <sys/types.h>
>   #include <sys/wait.h>
>   

Please add comments here about why we are adding this so there
won't be any confusion later.

> +#undef SCHED_NORMAL
> +#undef SCHED_FLAG_KEEP_ALL
> +#undef SCHED_FLAG_UTIL_CLAMP
> +
>   #include "../kselftest.h"
>   #include "../clone3/clone3_selftests.h"
>   

With that change:

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>

I am assuming this will go through Christian's tree. If not I can
take it through mine.

thanks,
-- Shuah

Re: [PATCH RFC] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Paul E. McKenney]

On Fri, Jul 18, 2025 at 03:03:43PM -0600, Shuah Khan wrote:
> On 7/14/25 17:01, Paul E. McKenney wrote:
> > The pidfd selftests run in userspace and include both userspace and kernel
> > header files.  On some distros (for example, CentOS), this results in
> > duplicate-symbol warnings in allmodconfig builds, while on other distros
> > (for example, Ubuntu) it does not.  (This happens in recent -next trees,
> > including next-20250714.)
> > 
> > Therefore, use #undef to get rid of the userspace definitions in favor
> > of the kernel definitions.
> > 
> > Other ways of handling this include splitting up the selftest code so
> > that the userspace definitions go into one translation unit and the
> > kernel definitions into another (which might or might not be feasible)
> > or to adjust compiler command-line options to suppress the warnings
> > (which might or might not be desirable).
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> > Cc: Christian Brauner <brauner@kernel.org>
> > Cc: Shuah Khan <shuah@kernel.org>
> > Cc: <linux-kselftest@vger.kernel.org>
> > 
> > ---
> >   pidfd.h |    4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
> > index efd74063126eb..6ff495398e872 100644
> > --- a/tools/testing/selftests/pidfd/pidfd.h
> > +++ b/tools/testing/selftests/pidfd/pidfd.h
> > @@ -16,6 +16,10 @@
> >   #include <sys/types.h>
> >   #include <sys/wait.h>
> 
> Please add comments here about why we are adding this so there
> won't be any confusion later.

Good point, thank you!

Like this?

/*
 * Remove the userspace definitions of the following preprocessor symbols
 * to avoid duplicate-definition warnings from the subsequent in-kernel
 * definitions.
 */

> > +#undef SCHED_NORMAL
> > +#undef SCHED_FLAG_KEEP_ALL
> > +#undef SCHED_FLAG_UTIL_CLAMP
> > +
> >   #include "../kselftest.h"
> >   #include "../clone3/clone3_selftests.h"
> 
> With that change:
> 
> Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>

Thank you!

> I am assuming this will go through Christian's tree. If not I can
> take it through mine.

I am of course good either way.  ;-)

							Thanx, Paul

[PATCH v2] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Paul E. McKenney]

The pidfd selftests run in userspace and include both userspace and kernel
header files.  On some distros (for example, CentOS), this results in
duplicate-symbol warnings in allmodconfig builds, while on other distros
(for example, Ubuntu) it does not.

Therefore, use #undef to get rid of the userspace definitions in favor
of the kernel definitions.

Other ways of handling this include splitting up the selftest code so
that the userspace definitions go into one translation unit and the
kernel definitions into another (which might or might not be feasible)
or to adjust compiler command-line options to suppress the warnings
(which might or might not be desirable).

[ paulmck: Apply Shuah Khan feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: <linux-kselftest@vger.kernel.org>

---
 pidfd.h |    9 +++++++++
 1 file changed, 9 insertions(+)

Changes since v1 (RFC):

o	Added comment explaining the purpose of the #undef calls per
	Shuah Khan feedback.

diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
index efd74063126eb..254eaa6cc4dfa 100644
--- a/tools/testing/selftests/pidfd/pidfd.h
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -16,6 +16,15 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
+/*
+ * Remove the userspace definitions of the following preprocessor symbols
+ * to avoid duplicate-definition warnings from the subsequent in-kernel
+ * definitions.
+ */
+#undef SCHED_NORMAL
+#undef SCHED_FLAG_KEEP_ALL
+#undef SCHED_FLAG_UTIL_CLAMP
+
 #include "../kselftest.h"
 #include "../clone3/clone3_selftests.h"
 

Re: [PATCH v2] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Shuah Khan]

On 7/23/25 17:13, Paul E. McKenney wrote:
> The pidfd selftests run in userspace and include both userspace and kernel
> header files.  On some distros (for example, CentOS), this results in
> duplicate-symbol warnings in allmodconfig builds, while on other distros
> (for example, Ubuntu) it does not.
> 
> Therefore, use #undef to get rid of the userspace definitions in favor
> of the kernel definitions.
> 
> Other ways of handling this include splitting up the selftest code so
> that the userspace definitions go into one translation unit and the
> kernel definitions into another (which might or might not be feasible)
> or to adjust compiler command-line options to suppress the warnings
> (which might or might not be desirable).
> 
> [ paulmck: Apply Shuah Khan feedback. ]

Looks good to me.

thanks,
-- Shuah

Re: [PATCH v2] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Shuah Khan]

On 7/24/25 12:26, Shuah Khan wrote:
> On 7/23/25 17:13, Paul E. McKenney wrote:
>> The pidfd selftests run in userspace and include both userspace and kernel
>> header files.  On some distros (for example, CentOS), this results in
>> duplicate-symbol warnings in allmodconfig builds, while on other distros
>> (for example, Ubuntu) it does not.
>>
>> Therefore, use #undef to get rid of the userspace definitions in favor
>> of the kernel definitions.
>>
>> Other ways of handling this include splitting up the selftest code so
>> that the userspace definitions go into one translation unit and the
>> kernel definitions into another (which might or might not be feasible)
>> or to adjust compiler command-line options to suppress the warnings
>> (which might or might not be desirable).
>>
>> [ paulmck: Apply Shuah Khan feedback. ]
> 
> Looks good to me.
>

I picked this up for Linux 6.17-rc1.

thanks,
-- Shuah

Re: [PATCH v2] selftests/pidfd: Fix duplicate-symbol warnings for SCHED_ CPP symbols

[Paul E. McKenney]

On Thu, Jul 24, 2025 at 04:17:07PM -0600, Shuah Khan wrote:
> On 7/24/25 12:26, Shuah Khan wrote:
> > On 7/23/25 17:13, Paul E. McKenney wrote:
> > > The pidfd selftests run in userspace and include both userspace and kernel
> > > header files.  On some distros (for example, CentOS), this results in
> > > duplicate-symbol warnings in allmodconfig builds, while on other distros
> > > (for example, Ubuntu) it does not.
> > > 
> > > Therefore, use #undef to get rid of the userspace definitions in favor
> > > of the kernel definitions.
> > > 
> > > Other ways of handling this include splitting up the selftest code so
> > > that the userspace definitions go into one translation unit and the
> > > kernel definitions into another (which might or might not be feasible)
> > > or to adjust compiler command-line options to suppress the warnings
> > > (which might or might not be desirable).
> > > 
> > > [ paulmck: Apply Shuah Khan feedback. ]
> > 
> > Looks good to me.
> 
> I picked this up for Linux 6.17-rc1.

Thank you, Shuah!

							Thanx, Paul