Quoting Steve Reinhardt <[email protected]>:
On Mon, Jan 2, 2012 at 12:19 PM, Nilay Vaish <[email protected]> wrote:
Step back a little... the problem you're having is in the way that
interrupts and squashing interact. You have fixed it by changing how
interrupts are handled, but it probably could also have been solved by
changing how squashing works (and I think that that was the direction you
were headed initially, talking about changes to the isSquashAfter flag).
I am not too confident that squashing working correctly can imply
interrupts are handled correctly. It might just work out. But as Gabe said
in one of his emails today, the condition for interrupt handling (instList
being empty) is broken. And this is independent of squashing.
I agree that it seems that the interrupt handling code is a little more to
blame, and your fix is probably the right thing to do (or at least it's
trying to do the right thing). But nevertheless, the problem it was
causing for you was in how it interacted with squashing.
Gabe is pointing out that there was an earlier, similar bug in the way that
branch mispredictions and squashing interacted, that probably also could
have been solved with changing how squashing works, in a way that probably
would have addressed your problem too.
I'm not saying anything about which solution is preferable, just trying to
get you and Gabe to see more eye-to-eye (and maybe get everyone else on
the
same page too).
Steve, I don't think there is much to gain from this argument. We should
rather focus our energies on getting the O3 CPU to work correctly. In fact,
I need yours and everyone elses opinion on those other threads (check
pointing, interrupt handling) that are open. Let's just agree that both
squashing and interrupt handling mechanisms are broken and that they need
to be fixed.
This was not intended to be an argument! It was intended to try and
explain to you why Gabe saw the problem you were running into as being
related to one he had already dealt with. It was not intended to come to
any other conclusion than, as I said, to get you and Gabe to see more
eye-to-eye and get everyone on the same page, so that future discussions
can benefit from a common understanding and not be hindered by lingering
beliefs that the person on the other side of the discussion doesn't know
what he is talking about. I hope you don't feel that that goal is unworthy
or impossible to achieve.
Steve
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I see what Nilay was talking about. These were two really similar
problems which were still not the same. If only the interrupt related
problems get fixed for now, that would be ok. It wouldn't just be
hacking around the other problem like I thought at first.
Gabe
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