Messages in this thread | | | Date | Wed, 27 Jun 2007 16:30:15 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [BUG] long freezes on thinkpad t60 |
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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
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