Patch "locking/lockdep: Add nest_lock integrity test" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

locking/lockdep: Add nest_lock integrity test

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
locking-lockdep-add-nest_lock-integrity-test.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Peter Zijlstra <[email protected]>
Date: Wed, 1 Mar 2017 16:23:30 +0100
Subject: locking/lockdep: Add nest_lock integrity test

From: Peter Zijlstra <[email protected]>

[ Upstream commit 7fb4a2cea6b18dab56d609530d077f168169ed6b ]

Boqun reported that hlock->references can overflow. Add a debug test for that to generate a clear error when this happens.

Without this, lockdep is likely to report a mysterious failure on unlock.

---
 kernel/locking/lockdep.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

@@ -3260,10 +3260,17 @@ static int __lock_acquire(struct lockdep
 	if (depth) {
 		hlock = curr->held_locks + depth - 1;
 		if (hlock->class_idx == class_idx && nest_lock) {
-			if (hlock->references)
+			if (hlock->references) {
+				/*
+				 * Check: unsigned int references:12, overflow.
+				 */
+				if (DEBUG_LOCKS_WARN_ON(hlock->references == (1 << 12)-1))
+					return 0;
+
 				hlock->references++;
-			else
+			} else {
 				hlock->references = 2;
+			}
 
 			return 1;
 		}

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/sched-fair-update-rq-clock-before-changing-a-task-s-cpu-affinity.patch queue-4.9/locking-lockdep-add-nest_lock-integrity-test.patch