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

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Date:   Mon, 21 Jun 2021 11:54:29 +0200
From:   Odin Ugedal <odin@...d.al>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Odin Ugedal <odin@...d.al>,
        Sachin Sant <sachinp@...ux.vnet.ibm.com>,
        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

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.


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*/