diff options
authorSerge Belyshev <>2007-10-04 23:10:04 +0200
committerLinus Torvalds <>2007-10-05 08:04:35 -0700
commit4ecbca8554d0f643351ee07d3284138a5e85ba81 (patch)
parent9cdcaa2c9330432bfe891d40f2d914b80bbcf9f3 (diff)
Remove unnecessary cast in prefetch()
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 paragraph 4 and note #84). prefetch() has a memory reference for its argument. 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. [ It seems in theory gcc 4.2 could miscompile this too; although no cases known. In 2.6.24 we should probably switch to __builtin_prefetch() instead, but this is a simpler fix for now. -- AK ] Signed-off-by: Serge Belyshev <> Signed-off-by: Andi Kleen <> Signed-off-by: Linus Torvalds <>
1 files changed, 1 insertions, 1 deletions
diff --git a/include/asm-x86_64/processor.h b/include/asm-x86_64/processor.h
index 19525175b91c..31f579b828f2 100644
--- a/include/asm-x86_64/processor.h
+++ b/include/asm-x86_64/processor.h
@@ -371,7 +371,7 @@ static inline void sync_core(void)
static inline void prefetch(void *x)
- asm volatile("prefetcht0 %0" :: "m" (*(unsigned long *)x));
+ asm volatile("prefetcht0 (%0)" :: "r" (x));