Messages in this thread |  | | Date | Wed, 10 Oct 2001 17:24:31 +0400 | From | Ivan Kokshaysky <> | Subject | Re: [Lse-tech] Re: RFC: patch to allow lock-free traversal of lists with insertion |
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On Wed, Oct 10, 2001 at 04:05:02AM +0200, Andrea Arcangeli wrote: > So before changing any code, I would prefer to double check with the > current alpha architects that the read dependency really isn't enough to > enforce read ordering without the need of rmb also on the beleeding edge > ev6/ev67/etc.. cores. So potentially as worse we'd need to redefine > wmb() as wmbdd() (and friends) only for EV5+SMP compiles of the kernel, > but we wouldn't be affected with any recent hardware compiling for > EV6/EV67. Jay, Peter, comments?
21264 Compiler Writer's Guide [appendix C] explicitly says that the second load cannot issue if its address depends on a result of previous load until that result is available. I refuse to believe that it isn't true for older alphas, especially because they are strictly in-order machines, unlike ev6.
I suspect some confusion here - probably that architect meant loads to independent addresses. Of course, in this case mb() is required to assure ordering.
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