On 2019/09/29 22:54, Greg Kroah-Hartman 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().
Please drop "[PATCH 4.19 36/63] locking/lockdep: Add debug_locks check in __lock_downgrade()". We had a revert patch shown below in the past.
"[PATCH 4.19 37/63] locking/lockdep: Add debug_locks check in __lock_downgrade() - again" seems the correct patch.
On 2019/04/25 17:08, gregkh@linuxfoundation.org wrote:>
This is a note to let you know that I've just added the patch titled
Revert "locking/lockdep: Add debug_locks check in __lock_downgrade()"to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: revert-locking-lockdep-add-debug_locks-check-in-__lock_downgrade.patch and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 7f437eec35a20f40d9ff82ae1c072b211c29e8e0 Mon Sep 17 00:00:00 2001
From: Greg Kroah-Hartman gregkh@linuxfoundation.org Date: Thu, 25 Apr 2019 10:00:43 +0200 Subject: Revert "locking/lockdep: Add debug_locks check in __lock_downgrade()"
From: Greg Kroah-Hartman gregkh@linuxfoundation.org
This reverts commit 0e0f7b30721233ce610bde2395a8e58ff7771475 which was commit 71492580571467fb7177aade19c18ce7486267f5 upstream.
Tetsuo rightly points out that the backport here is incorrect, as it touches the __lock_set_class function instead of the intended __lock_downgrade function.
Reported-by: Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp Cc: Waiman Long longman@redhat.com Cc: 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 Cc: Ingo Molnar mingo@kernel.org Cc: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
kernel/locking/lockdep.c | 3 --- 1 file changed, 3 deletions(-)
--- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3567,9 +3567,6 @@ __lock_set_class(struct lockdep_map *loc unsigned int depth; int i;
- if (unlikely(!debug_locks))
return 0;- depth = curr->lockdep_depth; /*
- This function is about (re)setting the class of a held lock,