lkml.org 
[lkml]   [2007]   [Sep]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH]: x86_64: Remove unnecessary cast in prefetch()
From
Date

It is ok to call prefetch() function with NULL argument, as specifically
commented in include/linux/prefetch.h. But in standard C, it is invalid to
dereference NULL pointer (see C99 standard 6.5.3.2 paragraph 4 and note #84).
Newer gcc versions (4.3 and above) will use that to conclude that "x"
argument is non-null and thus wreaking havok everywhere prefetch() was inlined.
Fixed by removing cast and changing asm constraint.

This can be fixed better by using gcc's __builtin_prefetch().

Signed-off-by: Serge Belyshev <belyshev@depni.sinp.msu.ru>

---
include/asm-x86_64/processor.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/include/asm-x86_64/processor.h
===================================================================
--- linux.orig/include/asm-x86_64/processor.h
+++ linux/include/asm-x86_64/processor.h
@@ -373,7 +373,7 @@ static inline void sync_core(void)
#define ARCH_HAS_PREFETCH
static inline void prefetch(void *x)
{
- asm volatile("prefetcht0 %0" :: "m" (*(unsigned long *)x));
+ asm volatile("prefetcht0 (%0)" :: "r" (x));
}

#define ARCH_HAS_PREFETCHW 1
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-09-06 23:55    [W:0.034 / U:0.508 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site