On Fri, 2013-05-03 at 15:29 +0100, David Laight wrote: > > > Could ppc64 experts confirm using byte is safe, or should we really add > > > a 32bit hole after the spinlock ? If so, I wonder how many other places > > > need a change... > ... > > Also I'd be surprised if ppc64 is the only one with that problem... what > > about sparc64 and arm64 ? > > Even x86 could be affected. > The width of the memory cycles used by the 'bit set and bit clear' > instructions isn't documented. They are certainly allowed to do > RMW on adjacent bytes. > I don't remember whether they are constrained to only do > 32bit accesses, but nothing used to say that they wouldn't > do 32bit misaligned ones! (although I suspect they never have).
x86 is not affected (or else we would have found the bug much earlier) Setting 1-bit field to one/zero uses OR/AND instructions. orb $4,724(%reg) doesn't load/store 64bits but 8bits. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev