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

From: Greg KH
Date: Tue Sep 10 2019 - 10:32:49 EST

On Thu, Sep 05, 2019 at 11:07:14AM +0800, Baolin Wang wrote:
> From: Waiman Long <longman@xxxxxxxxxx>
> [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@xxxxxxxxxxxxxxxxxxx>
> Reported-by: syzbot+53383ae265fb161ef488@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Link:
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Baolin Wang <>
> ---
> 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).


greg k-h