Re: [BACKPORT 4.14.y v2 2/6] locking/lockdep: Add debug_locks check in __lock_downgrade()

[Greg KH <greg@kroah.com>]

On Thu, Sep 05, 2019 at 11:07:14AM +0800, Baolin Wang wrote:
> From: Waiman Long <longman@redhat.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@i-love.sakura.ne.jp>
> Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com
> Signed-off-by: Waiman Long <longman@redhat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Will Deacon <will.deacon@arm.com>
> Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.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