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>
4ecbca8554