Messages in this thread | | | Date | Thu, 1 Dec 2022 15:21:06 -0500 | From | Alan Stern <> | Subject | Re: [PATCH] tools: memory-model: Make plain accesses carry dependencies |
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On Thu, Dec 01, 2022 at 05:21:45PM +0000, Jonas Oberhauser wrote: > Thanks a lot for the helpful and detailed comments! > Three minor points before I send a new patch: > > > even if W' or R' (or both!) is plain. > > The "is" sounds slightly weird to me in the sentence because the last part I read is > "(or both!)", so I would slightly prefer "are" here.
People are pretty casual about subject-verb number agreement these days (there's a growing tendency in English for people to make the verb agree with the last noun occurring in the subject rather than the subject as a whole), so that should be okay.
> > On the other hand, if you change the second "dependencies" to "ones" and "unmarked" to "plain", maybe the whole thing will fit on one line. > > It fits even if I changed the second dependencies to "those" instead of "ones", i.e., > (* Redefine dependencies to include those carried through plain accesses *) > > which I would prefer.
Fine.
> > if you replaced the whole conditional with a simple > > WRITE_ONCE(*y, *z2); > > then the litmus test would become an example of OOTA! > > In my opinion it is already an example of OOTA, which I would define as an > rfi | ctrl | addr | data | fence > cycle.
That's not an unreasonable point of view (if you put rfe rather than rfi), but to me OOTA suggests something more: a value arising as if by magic rather than as a result of a computation. In your version of the litmus test there is WRITE_ONCE(*y, 1), so it's a little understandable that you could end up with 1 as the final values of x and y. But in my version, no values get computed anywhere, so the final value of x and y might just as easily be 1 or 56789 -- it literally arises "out of thin air".
> Let me know if you agree with these deviations from your suggestion > and have a great time,
Yes; with those changes you can add:
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
> jonas > > PS: > > When a colon is followed by a clause (as opposed to a list), it is customary to capitalize the first letter of that clause, just like we capitalize the first letter at the start of a sentence. > > In German, we also capitalize after a colon; but my English teachers used to deduct many points throughout my adolescent life whenever I capitalized like that. I still remember some of that red ink with near perfect clarity. So I eventually really took it to heart and started pedantically not-capitalizing after every colon. > Now the only time it ever mattered in my adult life, I find that I should do it German Style (or, as I just learned, APA & AP Style). > I suppose life is that way sometimes.
Indeed.
Alan
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