linux-kernel - Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

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Message-ID: <20190515185257.GC2888@sultan-box.localdomain>
Date:   Wed, 15 May 2019 11:52:57 -0700
From:   Sultan Alsawaf <sultan@...neltoast.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Christian Brauner <christian@...uner.io>,
        Daniel Colascione <dancol@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        linux-mm <linux-mm@...ck.org>,
        kernel-team <kernel-team@...roid.com>,
        Andy Lutomirski <luto@...capital.net>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Kees Cook <keescook@...omium.org>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [RFC] simple_lmk: Introduce Simple Low Memory Killer for Android

On Wed, May 15, 2019 at 02:32:48PM -0400, Steven Rostedt wrote:
> I'm confused why you did this?

Oleg said that debug_locks_off() could've been called and thus prevented
lockdep complaints about simple_lmk from appearing. To eliminate any possibility
of that, I disabled debug_locks_off().

Oleg also said that __lock_acquire() could return early if lock debugging were
somehow turned off after lockdep reported one bug. To mitigate any possibility
of that as well, I threw in the BUG_ON() for good measure.

I think at this point it's pretty clear that lockdep truly isn't complaining
about simple_lmk's locking pattern, and that lockdep's lack of complaints isn't
due to it being mysteriously turned off...

Sultan