Commit 7fb4a2ce authored Mar 01, 2017 by Peter Zijlstra Committed by Ingo Molnar Mar 02, 2017

locking/lockdep: Add nest_lock integrity test



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.

Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 2b232e0c

kernel/locking/lockdep.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -3260,10 +3260,17 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
		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;
		}

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