Re: JavaMemoryModel: fusing synch blocks

From: Jerry Schwarz (
Date: Fri Feb 02 2001 - 20:25:09 EST

At 09:21 AM 02/02/2001, Doug Lea wrote:
> > * At a point where a thread releases a lock (in the original
> > program), if another thread of equal or higher priority is waiting on
> > the lock, the other thread should be allowed to obtain (perhaps we
> > need to limited this to "compete for") the lock within a short
> > interval.
>Well, I hope not to be too cynical or pessimistic about this, but I
>am. Last I knew, there are JVM providers who absolutely will not
>accept such rules. (I believe that similar issues arose in POSIX.) I
>think the best we could hope for universal acceptance of is
>probablistic weak fairness. ("probablistic" because anything based in
>part on spinlocks will rely in part on effectively random hardware

Oracle has a VM with a non-preemptive scheduler. We would object strongly
to any fairness constraints of any kind.

Yes, I know, there has to be some multi-processing in the system. In our
case it happens at the database session level which is above the VM.

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