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| author | Serge Belyshev <belyshev@depni.sinp.msu.ru> | 2007-10-04 23:10:04 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-05 08:04:35 -0700 |
| commit | 4ecbca8554d0f643351ee07d3284138a5e85ba81 (patch) | |
| tree | 06fd712d440bba74c7957736a9a804dd42e276a4 | |
| parent | 9cdcaa2c9330432bfe891d40f2d914b80bbcf9f3 (diff) | |
| download | lwn-4ecbca8554d0f643351ee07d3284138a5e85ba81.tar.gz lwn-4ecbca8554d0f643351ee07d3284138a5e85ba81.zip | |
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 6.5.3.2 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 <belyshev@depni.sinp.msu.ru>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/asm-x86_64/processor.h | 2 |
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) #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 |