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From:   Qian Cai <cai@lca.pw>
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Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk()
Date:   Tue, 8 Oct 2019 06:04:32 -0400
Message-Id: <298970BD-529E-4095-8D87-61470ADBDD32@lca.pw>
References: <20191008084031.GC6681@dhcp22.suse.cz>
Cc:     Petr Mladek <pmladek@suse.com>, akpm@linux-foundation.org,
        sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org,
        peterz@infradead.org, linux-mm@kvack.org,
        john.ogness@linutronix.de, david@redhat.com,
        linux-kernel@vger.kernel.org
In-Reply-To: <20191008084031.GC6681@dhcp22.suse.cz>
To:     Michal Hocko <mhocko@kernel.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Oct 8, 2019, at 4:40 AM, Michal Hocko <mhocko@kernel.org> wrote:
>=20
> 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 loc=
k orders everywhere. On the other hand, it make a little different to spend t=
oo much time arguing the authentic of those reproducible locdep splats, as e=
ven false positives could be as bad for developers where it would disable th=
e whole lockdep and mask off other true deadlock could happen later.=