linux-kernel - Re: Memory hotplug softlock issue

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Message-ID: <20181120015644.GA5727@MiWiFi-R3L-srv>
Date:   Tue, 20 Nov 2018 09:56:44 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Hugh Dickins <hughd@...gle.com>, Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        pifang@...hat.com, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, aarcange@...hat.com,
        Mel Gorman <mgorman@...e.de>
Subject: Re: Memory hotplug softlock issue

On 11/19/18 at 09:59pm, Michal Hocko wrote:
> On Mon 19-11-18 12:34:09, Hugh Dickins wrote:
> > I'm glad that I delayed, what I had then (migration_waitqueue instead
> > of using page_waitqueue) was not wrong, but what I've been using the
> > last couple of months is rather better (and can be put to use to solve
> > similar problems in collapsing pages on huge tmpfs. but we don't need
> > to get into that at this time): put_and_wait_on_page_locked().
> > 
> > What I have not yet done is verify it on latest kernel, and research
> > the interested Cc list (Linus and Tim Chen come immediately to mind),
> > and write the commit comment. I have some testing to do on the latest
> > kernel today, so I'll throw put_and_wait_on_page_locked() in too,
> > and post tomorrow I hope.
> 
> Cool, it seems that Baoquan has a reliable test case to trigger the
> pathological case.

Yes. I will test Hugh's patch.