[PATCH] introduce WARN_ON_ONCE(cond)

Add WARN_ON_ONCE(cond) to print once-per-bootup messages.

[rostedt@goodmis.org: improve code generation]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-generic/bug.h

@@ -38,4 +38,17 @@
 #endif
 #endif
 
+#define WARN_ON_ONCE(condition)				\
+({							\
+	static int __warn_once = 1;			\
+	int __ret = 0;					\
+							\
+	if (unlikely((condition) && __warn_once)) {	\
+		__warn_once = 0;			\
+		WARN_ON(1);				\
+		__ret = 1;				\
+	}						\
+	__ret;						\
+})
+
 #endif