On Tue, Dec 16, 2025 at 05:09:52PM +0530, Naresh Kamboju wrote:
The following boot warning is noticed on qemu-arm64 devices booting Linux next-20251215 on wards.
I didn't realise LKFT was operating from a hospital!
Regression Analysis:
- New regression? yes
- Reproducibility? yes
First seen on next-20251215 Bad: next-20251215 and next-20251216 Good: next-20251212
Boot regression: arm64: WARNING: kernel/sched/core.c:10851 at sched_change_end
This email is really painful to read, because the information is out-of-order and has random words added to obscure relevant information.
The warning you quote should be the *FIRST* line after you mention "The following boot warning".
That should be quoted *exactly* as the kernel logged it, without being prefixed by "Boot regression: arm64:", which the kernel didn't log, and which is redundant given the title and surrounding context.
It'd be *significantly* clearer to have:
| I'm seeing the following warning consistently on qemu-arm64 when | booting next-20251215 and later: | | WARNING: kernel/sched/core.c:10851 at sched_change_end | | Note: full splat at the end of this mail. | | First seen on next-20251215 | Bad: next-20251215 and next-20251216 | Good: next-20251212 | | This looks to be a regression.
... where someone can see all the relevant details at a glance.
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
$ git blame -L 10842 kernel/sched/core.c 5d1f0b2f278eb (Peter Zijlstra 2025-12-10 09:06:50 +0100 10842) ----> if (ctx->running && sched_class_above(p->sched_class, ctx->class)) { 5d1f0b2f278eb (Peter Zijlstra 2025-12-10 09:06:50 +0100 10843) rq->next_class->wakeup_preempt(rq, p, 0); 5d1f0b2f278eb (Peter Zijlstra 2025-12-10 09:06:50 +0100 10844) rq->next_class = p->sched_class; 5d1f0b2f278eb (Peter Zijlstra 2025-12-10 09:06:50 +0100 10845) } 5d1f0b2f278eb (Peter Zijlstra 2025-12-10 09:06:50 +0100 10846) 47efe2ddccb1f (Peter Zijlstra 2025-10-30 12:56:34 +0100 10847) /* 47efe2ddccb1f (Peter Zijlstra 2025-10-30 12:56:34 +0100 10848)
- If this was a degradation in class someone should have set
47efe2ddccb1f (Peter Zijlstra 2025-10-30 12:56:34 +0100 10849)
- need_resched by now.
47efe2ddccb1f (Peter Zijlstra 2025-10-30 12:56:34 +0100 10850) */ 47efe2ddccb1f (Peter Zijlstra 2025-10-30 12:56:34 +0100 10851) ----> WARN_ON_ONCE(sched_class_above(ctx->class, p->sched_class) && 47efe2ddccb1f (Peter Zijlstra 2025-10-30 12:56:34 +0100 10852) !test_tsk_need_resched(p)); 6455ad5346c9c (Peter Zijlstra 2024-11-01 14:16:10 +0100 10853) } else { 6455ad5346c9c (Peter Zijlstra 2024-11-01 14:16:10 +0100 10854) p->sched_class->prio_changed(rq, p, ctx->prio); 6455ad5346c9c (Peter Zijlstra 2024-11-01 14:16:10 +0100 10855) } f0e1a0643a59b (Tejun Heo 2024-06-18 10:09:17 -1000 10856) }
This is all formatted illegibly since it was line-wrapped, and you didn't mention why you're dumping this. AFAICT the only relevant bit is that the warning is from:
WARN_ON_ONCE(sched_class_above(ctx->class, p->sched_class) && !test_tsk_need_resched(p));
... which Peter added in commit:
47efe2ddccb1f ("sched/core: Add assertions to QUEUE_CLASS")
Have you tried looking around that commit, or bisecting?
[...]
Note: I've fixed the line-wrapping for the below. Please fix that in future.
[ 14.696414] ------------[ cut here ]------------ [ 14.696418] WARNING: kernel/sched/core.c:10851 at sched_change_end+0x168/0x188, CPU#12: ktimers/12/117 [ 14.729321] Modules linked in: cppc_cpufreq(+) arm_dsu_pmu(+) fuse drm backlight [ 14.736718] CPU: 12 UID: 0 PID: 117 Comm: ktimers/12 Not tainted 6.19.0-rc1-next-20251216 #1 PREEMPT_RT [ 14.746190] Hardware name: WIWYNN Mt.Jade Server System B81.030Z1.0010/Mt.Jade Motherboard, BIOS 2.10.20250506-1P (SCP: 2.10.20250506) 2025/05/06
This doesn't look like a "qemu-arm64 device" to me. Are you *sure* this wasn't bare-metal on a "WIWYNN Mt.Jade Server System"?
If not, why is QEMU passing that gunk to the guest!?
Mark.
[ 14.759217] pstate: 804000c9 (Nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 14.766169] pc : sched_change_end (kernel/sched/core.c:10851 (discriminator 7)) [ 14.770519] lr : sched_change_end (kernel/sched/core.c:10842 (discriminator 1)) [ 14.774781] sp : ffff800080d33b90 [ 14.778084] x29: ffff800080d33b90 x28: ffff07ff822f5500 x27: ffff80008e0c3660 [ 14.785213] x26: 00000000000000f0 x25: ffff07ff822f5500 x24: 0000000000000000 [ 14.792342] x23: 00000000ffffffff x22: ffffb4099c0d64d0 x21: ffff07ff822f5500 [ 14.799469] x20: ffff083e5eeaf140 x19: ffff083e5ee9b290 x18: 0000000000000000 [ 14.806597] x17: 0000000000000000 x16: ffffb4099a40ee68 x15: 0000000000000000 [ 14.813725] x14: 0000000000000000 x13: 0000000000000000 x12: 0000020000000000 [ 14.820853] x11: 00000000000000c0 x10: 0000000000000c60 x9 : ffffb40999b8d640 [ 14.827981] x8 : 000000000000000c x7 : ffff07ff92ad8400 x6 : 00000000ffffffff [ 14.835109] x5 : 00000000000000ee x4 : 000000036b338800 x3 : 000000036b33b800 [ 14.842238] x2 : 0000000000000001 x1 : ffffb4099c0d63d8 x0 : 0000000000000010 [ 14.849366] Call trace: [ 14.851802] sched_change_end (kernel/sched/core.c:10851 (discriminator 7)) (P) [ 14.856153] rt_mutex_setprio (kernel/sched/sched.h:1813 kernel/sched/core.c:7368) [ 14.860157] rt_mutex_slowunlock (kernel/locking/rtmutex.c:1341 kernel/locking/rtmutex.c:1466) [ 14.864422] rt_spin_unlock (kernel/locking/spinlock_rt.c:86) [ 14.868165] __hrtimer_run_queues (include/linux/spinlock_rt.h:44 kernel/time/hrtimer.c:1398 kernel/time/hrtimer.c:1843) [ 14.872513] hrtimer_run_softirq (kernel/time/hrtimer.c:579 kernel/time/hrtimer.c:1193 kernel/time/hrtimer.c:1861) [ 14.876600] handle_softirqs.isra.0 (arch/arm64/include/asm/jump_label.h:36 include/trace/events/irq.h:142 kernel/softirq.c:627) [ 14.881125] run_ktimerd (kernel/softirq.c:325 kernel/softirq.c:1144) [ 14.884520] smpboot_thread_fn (kernel/smpboot.c:160) [ 14.888608] kthread (kernel/kthread.c:463) [ 14.891828] ret_from_fork (arch/arm64/kernel/entry.S:861) [ 14.895396] ---[ end trace 0000000000000000 ]---
## Source
- Kernel version: 6.19.0-rc1
- Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
- Git commit: 4a5663c04bb679631985a15efab774da58c37815
- Git Describe: next-20251215
- Test Details: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20251215
## Boot details
- Boot log: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20251215/tes...
- Test details: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20251215/tes...
- Test plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/36sbHUVfnUK...
- Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/36sbH5DQckAagO0V1UEWB...
- Kernel config: https://storage.tuxsuite.com/public/linaro/lkft/builds/36sbH5DQckAagO0V1UEWB...
-- Linaro LKFT https://lkft.linaro.org