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>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 344e3091af24..d56fedbb457a 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))                         \