linux-kernel - Re: [PATCH v5] mm/oom_kill.c: futex: Close a race between do_exit and the oom

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Message-ID: <20220322004231.rwmnbjpq4ms6fnbi@offworld>
Date:   Mon, 21 Mar 2022 17:42:31 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Nico Pache <npache@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Rafael Aquini <aquini@...hat.com>,
        Waiman Long <longman@...hat.com>, Baoquan He <bhe@...hat.com>,
        Christoph von Recklinghausen <crecklin@...hat.com>,
        Don Dutile <ddutile@...hat.com>,
        "Herton R . Krzesinski" <herton@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Andre Almeida <andrealmeid@...labora.com>,
        David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joel Savitz <jsavitz@...hat.com>
Subject: Re: [PATCH v5] mm/oom_kill.c: futex: Close a race between do_exit
 and the oom_reaper

On Mon, 21 Mar 2022, Michal Hocko wrote:

>The more I am thinking about this the more I am getting convinced that
>we should rather approach this differently and skip over vmas which can
>be holding the list. Have you considered this option?

While I tend to agree with this over a hacky trylock approach, I cannot
help but think that v3 was the right thing to do, at least conceptually.
Robust futex users here care enough about dealing with crashes while holding
a lock that they sacrifice the performance of regular futexes. So the OOM
killer should not cause this very thing. I went through previous threads
but other than the user base (which I don't think would be very large
just because of the performance implications), was there any other reason
to no just set MMF_OOM_SKIP upon a robust list?

Thanks,
Davidlohr