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

From: Shrikanth Hegde <[email-masked]>
Date: Wed, 7 Jan 2026 10:21:53 +0530

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.

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.