linux-kernel - Re: [powerpc][5.13.0-rc7] Kernel warning (kernel/sched/fair.c:401) while running LTP tests

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Message-Id: <6D1F875D-58E9-4A55-B0C3-21D5F31EDB76@linux.vnet.ibm.com>
Date:   Mon, 21 Jun 2021 16:27:36 +0530
From:   Sachin Sant <sachinp@...ux.vnet.ibm.com>
To:     Odin Ugedal <odin@...d.al>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [powerpc][5.13.0-rc7] Kernel warning (kernel/sched/fair.c:401)
 while running LTP tests



> On 21-Jun-2021, at 3:24 PM, Odin Ugedal <odin@...d.al> wrote:
> 
> man. 21. jun. 2021 kl. 11:50 skrev Vincent Guittot <vincent.guittot@...aro.org>:
>> This means that a child's load was not null and it was inserted
>> whereas parent's load was null. This should not happen unless the
>> propagation failed somewhere
> 
> My initial thought is that the patch below will fix it, if that is the
> issue (that a leaf is inserted, but the propagation is not "completed"
> in unthrottle). Might that be the case? Still working on reproducing
> the issue tho.
> 

Unfortunately this does not help. I can still recreate the failure.

Have attached the o/p from test run.

Thanks
-Sachin
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index bfaa6e1f6067..015c5a5c1a4d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4930,12 +4930,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
>                if (cfs_rq_throttled(cfs_rq))
>                        goto unthrottle_throttle;
> 
> -               /*
> -                * One parent has been throttled and cfs_rq removed from the
> -                * list. Add it back to not break the leaf list.
> -                */
> -               if (throttled_hierarchy(cfs_rq))
> -                       list_add_leaf_cfs_rq(cfs_rq);
> +               list_add_leaf_cfs_rq(cfs_rq);
>        }
> 
>        /* At this point se is NULL and we are at root level*/

View attachment "run.txt" of type "text/plain" (5880 bytes)