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SubjectRe: [PATCH] sched: fix infinity loop in update_blocked_averages
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Hi Tejun,

On 2018/12/28 10:02, Tejun Heo wrote:
> On Thu, Dec 27, 2018 at 05:53:52PM -0800, Tejun Heo wrote:
>> Vincent knows that part way better than me but I think the safest way
>> would be doing the optimization removal iff tmp_alone_branch is
>> already pointing to leaf_cfs_rq_list. IIUC, it's pointing to
>> something else only while a branch is being built and deferring
>> optimization removal by an avg update cycle isn't gonna make any
>> difference anyway.
>
> So, something like the following. Xie, can you see whether the
> following patch resolves the problem?

Zhipeng is preparing to test it, thanks.

>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d1907506318a..88b9118b5191 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7698,7 +7698,8 @@ static void update_blocked_averages(int cpu)
> * There can be a lot of idle CPU cgroups. Don't let fully
> * decayed cfs_rqs linger on the list.
> */
> - if (cfs_rq_is_decayed(cfs_rq))
> + if (cfs_rq_is_decayed(cfs_rq) &&
> + rq->tmp_alone_branch == &rq->leaf_cfs_rq_list)
> list_del_leaf_cfs_rq(cfs_rq);
>
> /* Don't need periodic decay once load/util_avg are null */
>
> .
>

--
Thanks,
Xie XiuQi

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