From: Serge Belyshev Date: Thu, 4 Oct 2007 21:10:04 +0000 (+0200) Subject: Remove unnecessary cast in prefetch() X-Git-Tag: v2.6.23~29 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4ecbca8554d0f643351ee07d3284138a5e85ba81;p=linux-2.6 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 Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- diff --git a/include/asm-x86_64/processor.h b/include/asm-x86_64/processor.h index 19525175b9..31f579b828 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