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    SubjectRe: [PATCH v2] tools/memory-model: Add extra ordering for locks and remove it for ordinary release/acquire
    On Tue, 10 Jul 2018, Daniel Lustig wrote:

    > > --- usb-4.x.orig/tools/memory-model/linux-kernel.cat
    > > +++ usb-4.x/tools/memory-model/linux-kernel.cat
    > > @@ -38,7 +38,7 @@ let strong-fence = mb | gp
    > > (* Release Acquire *)
    > > let acq-po = [Acquire] ; po ; [M]
    > > let po-rel = [M] ; po ; [Release]
    > > -let rfi-rel-acq = [Release] ; rfi ; [Acquire]
    > > +let unlock-rf-lock-po = [UL] ; rf ; [LKR] ; po
    >
    > It feels slightly weird that unlock-rf-lock-po is asymmetrical. And in
    > fact, I think the current RISC-V solution we've been discussing (namely,
    > putting a fence.tso instead of a fence rw,w in front of the release)
    > may not even technically respect that particular sequence. The
    > fence.tso solution really enforces "po; [UL]; rf; [LKR]", right?
    >
    > Does something like "po; [UL]; rf; [LKR]; po" fit in with the rest
    > of the model? If so, maybe that solves the asymmetry and also
    > legalizes the approach of putting fence.tso in front?

    That would work just as well. For this version of the patch it
    doesn't make any difference, because nothing that comes po-after the
    LKR is able to directly read the value stored by the UL.

    Alan

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