Re: mips octeon memory model questions

From: Peter Zijlstra
Date: Tue Feb 04 2014 - 14:06:12 EST

On Tue, Feb 04, 2014 at 10:58:40AM -0800, Linus Torvalds wrote:
> On Tue, Feb 4, 2014 at 10:41 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> >
> > Still doesn't make sense, because if we need the first sync to stop
> > writes from being re-ordered with the ll-sc, we also need the second
> > sync to avoid the same.
> Presumably octeon doesn't do speculative writes, only *buffered* writes.

Speculative writes are bad.. :-)

> So writes move down, not up.

Right, but the ll-sc store might move down over a later store. Say
because the ll-sc needs to first get exclusive ownership of the
cacheline where the later store would be to an already owned line.

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