Subject: Re: [next-20251219]Build Failure on IBM Power system

From: Venkat Rao Bagalkote <[email-masked]>
Date: Fri, 9 Jan 2026 10:17:17 +0530

Hello Shrikanth,

On 07/01/26 10:21 am, Shrikanth Hegde wrote:
> Hi Venkat.
>
> On 1/1/26 10:50 AM, Venkat Rao Bagalkote wrote:
>> Greetings!!!
>>
>>
>> IBM CI has reported a build failure on next-20251219 build.
>>
>>
>> Build Failure:
>>
>> cc1: some warnings being treated as errors
>> make[4]: *** [scripts/Makefile.build:287: 
>> kernel/sched/build_policy.o] Error 1
>> make[4]: *** Waiting for unfinished jobs....
>> make[3]: *** [scripts/Makefile.build:556: kernel/sched] Error 2
>> make[3]: *** Waiting for unfinished jobs....
>> make[2]: *** [scripts/Makefile.build:556: kernel] Error 2
>> make[2]: *** Waiting for unfinished jobs....
>>
>
> Maddy had shared the failing log. Please share log like this in the 
> report.

Sure, Point taken.

>
> In file included from kernel/sched/build_policy.c:62:
> kernel/sched/ext.c: In function 'do_pick_task_scx':
> kernel/sched/ext.c:2470:27: error: implicit declaration of function 
> 'rq_modified_above' [-Wimplicit-function-declaration]
>  2470 |         if (!force_scx && rq_modified_above(rq, 
> &ext_sched_class))
>       |                           ^~~~~~~~~~~~~~~~~
> make[4]: *** [scripts/Makefile.build:287: kernel/sched/build_policy.o] 
> Error 1
>
>> IBM CI has bisected this issue to below commit.
>>
>>
>> 5d1f0b2f278eb55aebe29210fbc8f352c53497d6 is the first bad commit
>> commit 5d1f0b2f278eb55aebe29210fbc8f352c53497d6
>> Author: Peter Zijlstra <[email-masked]>
>> Date:   Wed Dec 10 09:06:50 2025 +0100
>>
>>
>> Bisection Logs:
>>
>> #git bisect log
>> git bisect log
>> git bisect start
>> # status: waiting for both good and bad commits
>> # good: [8f0b4cce4481fb22653697cced8d0d04027cb1e8] Linux 6.19-rc1
>> git bisect good 8f0b4cce4481fb22653697cced8d0d04027cb1e8
>> # status: waiting for bad commit, 1 good commit known
>> # bad: [cc3aa43b44bdb43dfbac0fcb51c56594a11338a8] Add linux-next 
>> specific files for 20251219
>> git bisect bad cc3aa43b44bdb43dfbac0fcb51c56594a11338a8
>> # good: [600a692707acda49434d6c2c03dda20f46e09749] Merge branch 
>> 'libcrypto-next' of https://git.kernel.org/pub/scm/linux/kernel/git/ 
>> ebiggers/linux.git
>> git bisect good 600a692707acda49434d6c2c03dda20f46e09749
>> # good: [816a7181ac38fd22243edb557537b2aecb9eeb76] Merge branch 
>> 'drm-xe- next' of https://gitlab.freedesktop.org/drm/xe/kernel.git
>> git bisect good 816a7181ac38fd22243edb557537b2aecb9eeb76
>> # good: [7157d55093613cf905cfd665772eae35d5c388f0] Merge branch 'for- 
>> next' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git
>> git bisect good 7157d55093613cf905cfd665772eae35d5c388f0
>> # bad: [52af2cfd69d264f1a370693966acf5d96943add8] Merge branch 
>> 'extcon- next' of 
>> https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/extcon.git
>> git bisect bad 52af2cfd69d264f1a370693966acf5d96943add8
>> # bad: [502068d3b65cc8695f8da83a7f19c90805c958ca] next-20251217/tip
>> git bisect bad 502068d3b65cc8695f8da83a7f19c90805c958ca
>> # bad: [c06f166058309936567065e737f6f5d9609a1a87] Merge branch into 
>> tip/ master: 'sched/core'
>> git bisect bad c06f166058309936567065e737f6f5d9609a1a87
>> # good: [e2292f5c21542354246687d8e3e48a58b046e27b] Merge branch into 
>> tip/master: 'irq/msi'
>> git bisect good e2292f5c21542354246687d8e3e48a58b046e27b
>> # good: [fb9a7458e508ef1beae8d80ee40c2cd1b5b45f3a] sched/fair: Clean 
>> up comments in 'struct cfs_rq'
>> git bisect good fb9a7458e508ef1beae8d80ee40c2cd1b5b45f3a
>> # good: [527a521029c3edd38fb9fc96cd58e3fd7393d28e] sched/fair: Sort 
>> out 'blocked_load*' namespace noise
>> git bisect good 527a521029c3edd38fb9fc96cd58e3fd7393d28e
>> # good: [7ac422cf7b16ec524bcd8e017459e328a4103f63] perf/x86/intel/ 
>> cstate: Add Diamond Rapids support
>> git bisect good 7ac422cf7b16ec524bcd8e017459e328a4103f63
>> # bad: [5d1f0b2f278eb55aebe29210fbc8f352c53497d6] sched/core: Rework 
>> sched_class::wakeup_preempt() and rq_modified_*()
>> git bisect bad 5d1f0b2f278eb55aebe29210fbc8f352c53497d6
>> # first bad commit: [5d1f0b2f278eb55aebe29210fbc8f352c53497d6] sched/ 
>> core: Rework sched_class::wakeup_preempt() and rq_modified_*()
>>
>>
>>
>> If you happen to fix this issue, please add below tag.
>>
>>
>> Reported-by: Venkat Rao Bagalkote <[email-masked]>
>>
>>
>>
>> Regards,
>>
>> Venkat.
>>
>>
>
> This seems like temporary some issue with merging.
>
> For example the problematic commit doesn't have the full patch as in 
> sched/core
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/kernel/sc[…]c?h=next-20251219&id=5d1f0b2f278eb55aebe29210fbc8f352c53497d6 
>
>
> I have checked the latest tag next-20260106. Full patch is there in that.
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/kernel/sched?h=next-20260106&id=704069649b5bfb7bf1fe32c0281fe9036806a59a 
>
>
> I have checked in tip/sched/core. There is no reference to 
> rq_modified_above.
>
> So, Fair to say we can ignore this report.

Thanks for the review and conforming. Looks like, this is fixed here.

https://lore.kernel.org/all/[email-masked]/

Regards,

Venkat.