linux-kernel - Re: [BACKPORT 4.14.y v2 2/6] locking/lockdep: Add debug_locks check in __lock

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Date:   Tue, 10 Sep 2019 15:32:42 +0100
From:   Greg KH <greg@...ah.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     stable@...r.kernel.org, peterz@...radead.org, mingo@...hat.com,
        longman@...hat.com, arnd@...db.de, orsonzhai@...il.com,
        vincent.guittot@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [BACKPORT 4.14.y v2 2/6] locking/lockdep: Add debug_locks check
 in __lock_downgrade()

On Thu, Sep 05, 2019 at 11:07:14AM +0800, Baolin Wang wrote:
> From: Waiman Long <longman@...hat.com>
> 
> [Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf]
> 
> Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
> warning right after a previous lockdep warning. It is likely that the
> previous warning turned off lock debugging causing the lockdep to have
> inconsistency states leading to the lock downgrade warning.
> 
> Fix that by add a check for debug_locks at the beginning of
> __lock_downgrade().
> 
> Reported-by: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
> Reported-by: syzbot+53383ae265fb161ef488@...kaller.appspotmail.com
> Signed-off-by: Waiman Long <longman@...hat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Will Deacon <will.deacon@....com>
> Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> ---
>  kernel/locking/lockdep.c |    3 +++
>  1 file changed, 3 insertions(+)

Why isn't this relevant for 4.19.y?  I can't add a patch to 4.14.y and
then have someone upgrade to 4.19.y and not have the same fix in there,
that would be a regression.

So can you redo this series also with a 4.19.y set at the same so we
don't get out of sync?  I've queued up your first patch already as that
was in 4.19.y (and also needed in 4.9.y).

thanks,

greg k-h