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

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Message-Id: <298970BD-529E-4095-8D87-61470ADBDD32@lca.pw>
Date:   Tue, 8 Oct 2019 06:04:32 -0400
From:   Qian Cai <cai@....pw>
To:     Michal Hocko <mhocko@...nel.org>
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 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. On the other hand, it make a little different to spend too much time arguing the authentic of those reproducible locdep splats, as even false positives could be as bad for developers where it would disable the whole lockdep and mask off other true deadlock could happen later.