linux-kernel - Re: [powerpc][next-20210621] WARNING at kernel/sched/fair.c:3277 during boot

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Message-Id: <5D874F72-B575-4830-91C3-8814A2B371CD@linux.vnet.ibm.com>
Date:   Wed, 23 Jun 2021 22:15:59 +0530
From:   Sachin Sant <sachinp@...ux.vnet.ibm.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>,
        Odin Ugedal <odin@...d.al>
Cc:     Linux Next Mailing List <linux-next@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [powerpc][next-20210621] WARNING at kernel/sched/fair.c:3277
 during boot

> Ok. This becomes even more weird. Could you share your config file and more details about
> you setup ?
> 
> Have you applied the patch below ? 
> https://lore.kernel.org/lkml/20210621174330.11258-1-vincent.guittot@linaro.org/
> 
> Regarding the load_avg warning, I can see possible problem during attach. Could you add
> the patch below. The load_avg warning seems to happen during boot and sched_entity
> creation.
> 

Here is a summary of my testing. 

I have a POWER box with PowerVM hypervisor. On this box I have a logical partition(LPAR) or guest
(allocated with 32 cpus 90G memory) running linux-next. 

I started with a clean slate.
Moved to linux-next 5.13.0-rc7-next-20210622 as base code.
Applied patch #1 from Vincent which contains changes to dequeue_load_avg()
Applied patch #2 from Vincent which contains changes to enqueue_load_avg()
Applied patch #3 from Vincent which contains changes to attach_entity_load_avg()
Applied patch #4 from https://lore.kernel.org/lkml/20210621174330.11258-1-vincent.guittot@linaro.org/

With these changes applied I was still able to recreate the issue. I could see kernel warning
during boot.

I then applied patch #5 from Odin which contains changes to update_cfs_rq_load_avg()

With all the 5 patches applied I was able to boot the kernel without any warning messages.
I also ran scheduler related tests from ltp (./runltp -f sched) . All tests including cfs_bandwidth01
ran successfully. No kernel warnings were observed.

Have also attached .config in case it is useful. config has CONFIG_HZ_100=y

Thanks
-Sachin

View attachment "config_next_powerpc.txt" of type "text/plain" (179600 bytes)