linux-kernel - Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk()

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Message-ID: <20191008103907.GE6681@dhcp22.suse.cz>
Date:   Tue, 8 Oct 2019 12:39:07 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Qian Cai <cai@....pw>
Cc:     Petr Mladek <pmladek@...e.com>, akpm@...ux-foundation.org,
        sergey.senozhatsky.work@...il.com, rostedt@...dmis.org,
        peterz@...radead.org, linux-mm@...ck.org,
        john.ogness@...utronix.de, david@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk()

On Tue 08-10-19 06:04:32, Qian Cai wrote:
> 
> 
> > On Oct 8, 2019, at 4:40 AM, Michal Hocko <mhocko@...nel.org> wrote:
> > 
> > Does this tip point to a real deadlock or merely a class of lockdep
> > false dependencies?
> 
> I lean towards it is a real deadlock given how trivial to generate those lock orders everywhere.

Have you actually triggered any real deadlock? With a zone->lock in
place it would be pretty clear with hard lockups detected.

-- 
Michal Hocko
SUSE Labs