linux-kernel - Re: [PATCH v3] memcg: fix soft lockup in the OOM process

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Message-ID: <Z4YunYyj6oqmdrUt@tiehlicka>
Date: Tue, 14 Jan 2025 10:30:05 +0100
From: Michal Hocko <mhocko@...e.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Chen Ridong <chenridong@...weicloud.com>, hannes@...xchg.org,
	yosryahmed@...gle.com, roman.gushchin@...ux.dev,
	shakeel.butt@...ux.dev, muchun.song@...ux.dev, davidf@...eo.com,
	handai.szj@...bao.com, rientjes@...gle.com,
	kamezawa.hiroyu@...fujitsu.com, RCU <rcu@...r.kernel.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org, chenridong@...wei.com,
	wangweiyang2@...wei.com
Subject: Re: [PATCH v3] memcg: fix soft lockup in the OOM process

On Tue 14-01-25 10:20:28, Vlastimil Babka wrote:
> On 1/14/25 09:40, Michal Hocko wrote:
> > On Mon 13-01-25 19:45:46, Andrew Morton wrote:
[...]
> >> > For global OOM, system is likely to struggle, do we have to do some
> >> > works to suppress RCU detete?
> >> 
> >> rcu_cpu_stall_reset()?
> > 
> > Do we really care about those? The code to iterate over all processes
> > under RCU is there (basically) since ever and yet we do not seem to have
> > many reports of stalls? Chen's situation is specific to memcg OOM and
> > touching the global case was mostly for consistency reasons.
> 
> Then I'd rather not touch the global case then if it's theoretical?

No strong opinion on this on my side. The only actual reason
touch_softlockup_watchdog is there is becuase it originally had
incorrectly cond_resched there. If half silencing (soft lock up
detector only) disturbs people then let's just drop that hunk.
-- 
Michal Hocko
SUSE Labs