From b1ae345d971664f70cfdc293029c40ccfb093591 Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@intel.com>
Date: Thu, 21 Feb 2013 16:42:47 -0800
Subject: [PATCH] lockdep: make lockdep_assert_held() not have a return value

I recently made the mistake of writing:

  foo = lockdep_dereference_protected(..., lockdep_assert_held(...));

which is clearly bogus.  If lockdep is disabled in the config this would
cause a compile failure, if it is enabled then it compiles and causes a
puzzling warning about dereferencing without the correct protection.

Wrap the macro in "do { ...  } while (0)" to also fail compile for this
when lockdep is enabled.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/lockdep.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 2bca44b0893c..bfe88c4aa251 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -359,7 +359,9 @@ extern void lockdep_trace_alloc(gfp_t mask);
 
 #define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
 
-#define lockdep_assert_held(l)	WARN_ON(debug_locks && !lockdep_is_held(l))
+#define lockdep_assert_held(l)	do {				\
+		WARN_ON(debug_locks && !lockdep_is_held(l));	\
+	} while (0)
 
 #define lockdep_recursing(tsk)	((tsk)->lockdep_recursion)
 
-- 
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