linux-kernel - Re: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems

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Message-ID: <0e5ca6ee-d460-db8e-aba2-79aa7a66fad1@I-love.SAKURA.ne.jp>
Date:   Wed, 11 Mar 2020 07:05:40 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems

On 2020/03/11 6:39, David Rientjes wrote:
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2637,6 +2637,8 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
>  		unsigned long reclaimed;
>  		unsigned long scanned;
>  
> +		cond_resched();
> +

Is this safe for CONFIG_PREEMPTION case? If current thread has realtime priority,
can we guarantee that the OOM victim (well, the OOM reaper kernel thread rather
than the OOM victim ?) gets scheduled?

>  		switch (mem_cgroup_protected(target_memcg, memcg)) {
>  		case MEMCG_PROT_MIN:
>  			/*
>