Messages in this thread | | | Date | Mon, 22 Nov 2004 20:34:44 -0500 | From | john cooper <> | Subject | Re: Priority Inheritance Test (Real-Time Preemption) |
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Bill Huey (hui) wrote: > On Mon, Nov 22, 2004 at 09:16:18AM -0500, john cooper wrote: > >>I'd hazard a guess the reason existing implementations do not >>do this type of dependency-chain closure is the complexity of a >>general approach. Getting correct behavior and scaling on SMP >>require some restrictions of how lock ownership is maintained, >>otherwise fine grained locking is not possible. Another likely > > > What do you mean by that ? Are you talking about strict priority > obedience by the system ?
Not quite if I understand your question. I was referring to avoiding having a global lock to synchronize the conglomerate data structure when doing a PI dependency walk. The problem is the lock must be acquired not only in PI scenarios but in any case which may possibly lead to one or affect a concurrent PI in progress.
True this global lock is mostly an issue for large count SMP systems. But as witnessed by such voodoo[1] mechanisms as rcu, scalability problems are real at that end of the spectrum.
-john
[1] in a 'nice' way.
-- john.cooper@timesys.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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