[Xenomai-core] First thoughts on fast xnsynch

[Jan Kiszka <jan.kiszka@domain.hid>]

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Hi Gilles,

I spent a few brain cycles on the design of a generic fast-lock via
xnsynch. The first thing was defining the lock word and going through
its use cases.

You suggested to realize lock stealing directly in user space, but I
don't see now how this should work reasonably. Our problem is that we
would have to atomically check for the woken state AND compare the
current priority against the owner ones. Imaginable only if we replicate
the priorities into the lock word - but this makes things at least
horribly complicated (e.g. when priorities change). So I think we have
to drop this goal. Or what did you have in mind?

Jan


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