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SubjectRe: Serious problem with ticket spinlocks on ia64
Date
On Friday 27 of August 2010 23:11:55 Luck, Tony wrote:
> > One more idea. The wrap-around case is the only one when the high word is
> > modified. This is in fact the only case when the fetchadd.acq competes
> > with the st2.rel about the actual contents of that location. I don't know
> > if it matters...
>
> I pondered that for a while - but I have difficulty believing that
> fetchadd looks at which bits changed and only writes back the bytes
> that did.

OTOH the counter is only 15-bit, so it also wraps around at 0xfffe7fff, but
I have never seen it fail there. It always fails after the wrap-around from
0xfffeffff.

Petr Tesarik


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