From: Linus Torvalds <torvalds@woody.linux-foundation.org>
Date: Wed, 1 Aug 2007 04:12:07 +0000 (-0700)
Subject: Fix WARN_ON() on bitfield ops
X-Git-Tag: v2.6.23-rc2~28
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=8d4fbcfbe0a4bfc73e7f0297c59ae514e1f1436f;p=linux-2.6-omap-h63xx.git

Fix WARN_ON() on bitfield ops

Alexey Dobriyan noticed that the new WARN_ON() semantics that were
introduced by commit 684f978347deb42d180373ac4c427f82ef963171 (to also
return the value to be warned on) didn't compile when given a bitfield,
because the typeof doesn't work for bitfields.

So instead of the typeof trick, use an "int" variable together with a
"!!(x)" expression, as suggested by Al Viro.

To make matters more interesting, Paul Mackerras points out that that is
sub-optimal on Power, but the old asm-coded comparison seems to be buggy
anyway on 32-bit Power if the conditional was 64-bit, so I think there
are more problems there.

Regardless, the new WARN_ON() semantics may have been a bad idea.  But
this at least avoids the more serious complications.

Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 344e3091af2..d56fedbb457 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -33,7 +33,7 @@ struct bug_entry {
 
 #ifndef HAVE_ARCH_WARN_ON
 #define WARN_ON(condition) ({						\
-	typeof(condition) __ret_warn_on = (condition);			\
+	int __ret_warn_on = !!(condition);				\
 	if (unlikely(__ret_warn_on)) {					\
 		printk("WARNING: at %s:%d %s()\n", __FILE__,		\
 			__LINE__, __FUNCTION__);			\
@@ -54,7 +54,7 @@ struct bug_entry {
 
 #ifndef HAVE_ARCH_WARN_ON
 #define WARN_ON(condition) ({						\
-	typeof(condition) __ret_warn_on = (condition);			\
+	int __ret_warn_on = !!(condition);				\
 	unlikely(__ret_warn_on);					\
 })
 #endif
@@ -62,7 +62,7 @@ struct bug_entry {
 
 #define WARN_ON_ONCE(condition)	({				\
 	static int __warned;					\
-	typeof(condition) __ret_warn_once = (condition);	\
+	int __ret_warn_once = !!(condition);			\
 								\
 	if (unlikely(__ret_warn_once))				\
 		if (WARN_ON(!__warned)) 			\
diff --git a/include/asm-powerpc/bug.h b/include/asm-powerpc/bug.h
index a248b8bd4d7..e55d1f66b86 100644
--- a/include/asm-powerpc/bug.h
+++ b/include/asm-powerpc/bug.h
@@ -93,7 +93,7 @@
 } while (0)
 
 #define WARN_ON(x) ({						\
-	typeof(x) __ret_warn_on = (x);				\
+	int __ret_warn_on = !!(x);				\
 	if (__builtin_constant_p(__ret_warn_on)) {		\
 		if (__ret_warn_on)				\
 			__WARN();				\