[PATCH] lockdep: add DECLARE_COMPLETION_ONSTACK() API

lockdep needs to have the waitqueue lock initialized for on-stack waitqueues
implicitly initialized by DECLARE_COMPLETION().  Introduce the API.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/include/linux/completion.h b/include/linux/completion.h
index 90663ad217f9..251c41e3ddd5 100644
--- a/include/linux/completion.h
+++ b/include/linux/completion.h
@@ -21,6 +21,18 @@ struct completion {
 #define DECLARE_COMPLETION(work) \
         struct completion work = COMPLETION_INITIALIZER(work)
 
+/*
+ * Lockdep needs to run a non-constant initializer for on-stack
+ * completions - so we use the _ONSTACK() variant for those that
+ * are on the kernel stack:
+ */
+#ifdef CONFIG_LOCKDEP
+# define DECLARE_COMPLETION_ONSTACK(work) \
+        struct completion work = ({ init_completion(&work); work; })
+#else
+# define DECLARE_COMPLETION_ONSTACK(work) DECLARE_COMPLETION(work)
+#endif
+
 static inline void init_completion(struct completion *x)
 {
         x->done = 0;