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

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Date:   Tue, 10 Mar 2020 15:55:41 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
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 Wed, 11 Mar 2020, Tetsuo Handa 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?
> 

I think it's the best we can do that immediately solves the issue unless 
you have another idea in mind?

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