linux-kernel - Re: [PATCH v1] memcg: fix soft lockup in the OOM process

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Message-ID: <Z2F0ixNUW6kah1pQ@tiehlicka>
Date: Tue, 17 Dec 2024 13:54:35 +0100
From: Michal Hocko <mhocko@...e.com>
To: Chen Ridong <chenridong@...weicloud.com>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, yosryahmed@...gle.com,
	roman.gushchin@...ux.dev, shakeel.butt@...ux.dev,
	muchun.song@...ux.dev, davidf@...eo.com, vbabka@...e.cz,
	handai.szj@...bao.com, rientjes@...gle.com,
	kamezawa.hiroyu@...fujitsu.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	chenridong@...wei.com, wangweiyang2@...wei.com
Subject: Re: [PATCH v1] memcg: fix soft lockup in the OOM process

On Tue 17-12-24 12:18:28, Chen Ridong wrote:
[...]
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 1c485beb0b93..14260381cccc 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -390,6 +390,7 @@ static int dump_task(struct task_struct *p, void *arg)
>  	if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
>  		return 0;
>  
> +	cond_resched();
>  	task = find_lock_task_mm(p);
>  	if (!task) {
>  		/*

This is called from RCU read lock for the global OOM killer path and I
do not think you can schedule there. I do not remember specifics of task
traversal for crgoup path but I guess that you might need to silence the
soft lockup detector instead or come up with a different iteration
scheme.
-- 
Michal Hocko
SUSE Labs