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

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Date:   Wed, 15 May 2019 14:32:48 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Sultan Alsawaf <sultan@...neltoast.com>
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, 15 May 2019 10:27:28 -0700
Sultan Alsawaf <sultan@...neltoast.com> wrote:

> On Wed, May 15, 2019 at 04:58:32PM +0200, Oleg Nesterov wrote:
> > Could you explain in detail what exactly did you do and what do you see in dmesg?
> > 
> > Just in case, lockdep complains only once, print_circular_bug() does debug_locks_off()
> > so it it has already reported another false positive __lock_acquire() will simply
> > return after that.
> > 
> > Oleg.  
> 
> This is what I did:
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 774ab79d3ec7..009e7d431a88 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -3078,6 +3078,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
>         int class_idx;
>         u64 chain_key;
> 
> +       BUG_ON(!debug_locks || !prove_locking);
>         if (unlikely(!debug_locks))
>                 return 0;
> 
> diff --git a/lib/debug_locks.c b/lib/debug_locks.c
> index 124fdf238b3d..4003a18420fb 100644
> --- a/lib/debug_locks.c
> +++ b/lib/debug_locks.c
> @@ -37,6 +37,7 @@ EXPORT_SYMBOL_GPL(debug_locks_silent);
>   */
>  int debug_locks_off(void)
>  {
> +       return 0;

I'm confused why you did this?

-- Steve

>         if (debug_locks && __debug_locks_off()) {
>                 if (!debug_locks_silent) {
>                         console_verbose();
> 
>