From b42e737e576339c795d9ac77a1fce6057f6bc0cf Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon, 11 Aug 2008 12:34:42 +0200
Subject: [PATCH] lockdep: fix overflow in the hlock shrinkage code
There is a overflow by 1 case in the new shrunken hlock code.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/linux/lockdep.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 67f42b300c65..c88aa3d8e87f 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -191,7 +191,12 @@ struct lock_chain {
};
#define MAX_LOCKDEP_KEYS_BITS 11
-#define MAX_LOCKDEP_KEYS (1UL << MAX_LOCKDEP_KEYS_BITS)
+/*
+ * Subtract one because we offset hlock->class_idx by 1 in order
+ * to make 0 mean no class. This avoids overflowing the class_idx
+ * bitfield and hitting the BUG in hlock_class().
+ */
+#define MAX_LOCKDEP_KEYS ((1UL << MAX_LOCKDEP_KEYS_BITS) - 1)
struct held_lock {
/*
--
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