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Date: Mon, 25 Aug 2008 22:19:01 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: [Xenomai-core] xnregistry_fetch & friends
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Hi,

trying to select a sane kernel-side looking scheme for fast native
mutexes, I had a closer look at the registry usage in that skin (and
many others). The typical pattern is

object =3D xnregistry_fetch(handle);
perform_operation(object);

There is no lock around those two, both services do nklock acquisition
only internally. So this is a bit racy against concurrent object
destruction and memory releasing / object reconstruction. Well, I guess
the rational is: we test against object magics and the underlying memory
is normally not vanishing (immediately) on destruction, right? Remains
just object reconstruction. Not a real-life issue?

But then I wonder

 a) why xnregistry_fetch uses nklock at all (even for totally uncritical
    XNOBJECT_SELF!)

 b) what the ideas/plans on unused xnregistry_put/get are.

Jan


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