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SubjectRe: Merging relayfs?
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Tom Zanussi <zanussi@us.ibm.com> wrote on 14/07/2005 16:01:25:


> The only things that are atomic are the counts of produced and
> consumed buffers and these are only ever updated or read in the slow
> buffer-switch path. They're atomic because if they weren't, wouldn't
> it be possible for the client to read an unfinished value if the
> producer was in the middle of updating it?


This depends on architecture. It is possible under some architectures to
see the so-called score-boarding effect when reading on one processor while
writing on another when not having imposed any atomicity. From memory, I
believe this might be possible with zSeries, but I'll need to check the
microarchitecture docs. It's been a long time since I read them but I do
recall a reference to the score-boarding effect.


> ...


Richard


- -
Richard J Moore
IBM Advanced Linux Response Team - Linux Technology Centre
MOBEX: 264807; Mobile (+44) (0)7739-875237
Office: (+44) (0)1962-817072

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