On Tue, Jun 07, 2016 at 08:23:15AM -0700, Paul E. McKenney wrote: > On Tue, Jun 07, 2016 at 04:59:02PM +0200, Hannes Frederic Sowa wrote: > > Sorry, to follow-up again on this. Will Deacon's comments were about > > conditional-move instructions, which this compiler-option would prevent, > > as far as I can see it. > > According to this email thread, I believe that this works the other > way around: > > http://thread.gmane.org/gmane.linux.kernel/1721993 > > That parameter prevents the compiler from converting a conditional > store into an unconditional store, which would be really problematic. > Give the current kernel build, I believe that the compiler really is > within its rights to use conditional-move instructions as shown above. > But I again must defer to Will Deacon on the details. A multi_v7_defconfig build of mainline certainly spits out conditional store instructions, but I have no idea whether these correspond to WRITE_ONCE or not: $ objdump -d vmlinux | grep 'str\(eq\|ne\)' | wc -l 7326 At the end of the day, the ARM architecture says you can't rely on this being ordered and I can see it happening in practice in the face of conditional stores. Will -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
