On Wed, 27 Jun 2007, Linus Torvalds wrote: > > IOW shouldn't an mfence always be there? Not only loads could leak up > > into the wait phase, but stores too, if they have no dependency with the > > "head" and "tail" loads. > > Stores never "leak up". They only ever leak down (ie past subsequent loads > or stores), so you don't need to worry about them. That's actually already > documented (although not in those terms), and if it wasn't true, then we > couldn't do the spin unlock with just a regular store anyway.
Yes, Intel has never done that. They'll probably never do it since it'll break a lot of system software (unless they use a new mode-bit that allows system software to enable lose-ordering). Although I clearly remember to have read in one of their P4 optimization manuals to not assume this in the future. - Davide - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
