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

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Message-Id: <43AC5AD1-377D-447C-A703-7F10423E6FA0@lca.pw>
Date:   Tue, 8 Oct 2019 05:32:15 -0400
From:   Qian Cai <cai@....pw>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Michal Hocko <mhocko@...nel.org>,
        sergey.senozhatsky.work@...il.com, rostedt@...dmis.org,
        peterz@...radead.org, linux-mm@...ck.org,
        john.ogness@...utronix.de, akpm@...ux-foundation.org,
        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 4:15 AM, Petr Mladek <pmladek@...e.com> wrote:
> 
> I am curious about CPU2. Does scheduler need to allocate memory?

It happens before with debug objects. It might not 100% necessary but it could easily end up with this way in the current code. Moreover, this is just an example of how things could go wrong as it could happen for pi_lock or any other unknown downstream locks which are not really console related.