From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Tejun Heo <tj@kernel.org>
Cc: Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm,page_alloc: PF_WQ_WORKER threads must sleep at should_reclaim_retry().
Date: Mon, 30 Jul 2018 16:46:47 +0200 [thread overview]
Message-ID: <20180730144647.GX24267@dhcp22.suse.cz> (raw)
In-Reply-To: <9158a23e-7793-7735-e35c-acd540ca59bf@i-love.sakura.ne.jp>
On Mon 30-07-18 23:34:23, Tetsuo Handa wrote:
> On 2018/07/30 18:32, Michal Hocko wrote:
[...]
> > This one is waiting for draining and we are in mm_percpu_wq WQ context
> > which has its rescuer so no other activity can block us for ever. So
> > this certainly shouldn't deadlock. It can be dead slow but well, this is
> > what you will get when your shoot your system to death.
>
> We need schedule_timeout_*() to allow such WQ_MEM_RECLAIM workqueues to wake up. (Tejun,
> is my understanding correct?) Lack of schedule_timeout_*() does block WQ_MEM_RECLAIM
> workqueues forever.
Hmm. This doesn't match my understanding of what WQ_MEM_RECLAIM actually
guarantees. If you are right then the whole thing sounds quite fragile
to me TBH.
Anyway we would at least have an explanation for what you are seeing.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-07-30 14:46 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-26 11:06 Tetsuo Handa
2018-07-26 11:39 ` Michal Hocko
2018-07-27 15:47 ` Tetsuo Handa
2018-07-30 9:32 ` Michal Hocko
2018-07-30 14:34 ` Tetsuo Handa
2018-07-30 14:46 ` Michal Hocko [this message]
2018-07-30 14:54 ` Tejun Heo
2018-07-30 15:25 ` Tetsuo Handa
2018-07-30 15:44 ` Tejun Heo
2018-07-30 18:51 ` Michal Hocko
2018-07-30 19:10 ` Michal Hocko
2018-07-30 21:01 ` Tetsuo Handa
2018-07-31 5:09 ` Michal Hocko
2018-07-31 10:47 ` Tetsuo Handa
2018-07-31 11:15 ` Michal Hocko
2018-07-31 11:30 ` Tetsuo Handa
2018-07-31 11:55 ` Michal Hocko
2018-08-02 22:05 ` Tetsuo Handa
2018-08-03 6:16 ` Michal Hocko
2018-08-21 21:07 ` Tetsuo Handa
2018-08-22 7:32 ` Michal Hocko
2018-08-23 20:06 ` David Rientjes
2018-08-23 21:00 ` Tetsuo Handa
2018-08-23 22:45 ` David Rientjes
2018-08-24 0:31 ` Tetsuo Handa
2018-09-05 13:20 ` Tetsuo Handa
2018-09-05 13:40 ` Michal Hocko
2018-09-05 13:53 ` Tetsuo Handa
2018-09-05 14:04 ` Michal Hocko
2018-09-06 1:00 ` Tetsuo Handa
2018-09-06 5:57 ` Michal Hocko
2018-09-06 6:22 ` Tetsuo Handa
2018-09-06 7:03 ` Tetsuo Handa
2018-07-30 19:14 ` Tejun Heo
2018-08-27 13:51 Michal Hocko
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