Re: [sched/pelt] e906550aca: WARNING:at_kernel/sched/fair.c:#update_blocked_averages

[Vincent Guittot]

Hi Dietmar,

On Thu, 3 Jun 2021 at 12:50, Dietmar Eggemann <dietmar.eggemann@xxxxxxx> wrote:
>
> On 02/06/2021 08:45, kernel test robot wrote:
>
> [...]
>
> > kern :warn : [   40.989618] WARNING: CPU: 2 PID: 253 at kernel/sched/fair.c:8029 update_blocked_averages (kbuild/src/consumer/kernel/sched/fair.c:8029 kbuild/src/consumer/kernel/sched/fair.c:8065 kbuild/src/consumer/kernel/sched/fair.c:8152)
>
> Hit something like this on my Ubuntu i7-7567U as well.

Thanks for having a look at this.

>
> With more debugging:
>
> [    7.388006] WARNING: CPU: 1 PID: 926 at kernel/sched/fair.c:8029 update_blocked_averages+0x30d/0x7e0
> ...
> [    7.388167] path=/autogroup-2 load_avg=1 util_avg=0 runnable_avg=1
>
> IMHO, this is because this patch needs:
>
> (1) sched/pelt: ensure that *_sum is always synced with *_avg (2021-06-03 Vincent Guittot)
>
> https://lkml.kernel.org/r/20210601085832.12626-1-vincent.guittot@xxxxxxxxxx
>
> (2) sched/fair: Keep load_avg and load_sum synced (2021-06-03 Vincent Guittot)
>
> tip/sched/urgent 7c7ad626d9a0
>
> Using both patches underneath makes this warning go away.

I haven't spent time on this but that's also my 1st guess for the root cause

Regards,
Vincent

>