Re: JavaMemoryModel: Proposals on wait and interrupts

From: Joe Hendrix (
Date: Mon May 26 2003 - 15:49:47 EDT

Bill Pugh wrote:
> Proposal 1: a thread performing a wait should prefer throwing an IE over
> returning normally.

With spurius interrupts, it doesn't seem like anything useful can be
formally said about this property. A good implementation should
probably do this, but I don't see how the spec can say anything beyond
that if a thread has been interrupted before entering a wait, then
wait() will throw an InterruptedException.

> Proposal 2: if a thread T1 performing a wait on object m is removed from
> the wait set via a call to m.notify(), and T1 exits the call to wait by
> throwing an IE, then the VM should ensure that another m.notify() is
> performed.

The alternative is simply to not allow a thread to return with an
InterruptedException if it has been removed from the wait set via a notify.

Overall, from a practical standpoint, I don't think it is important that
  in Sylvia's example that thread 2 is woken up and not thread 3.
Waking up thread 3 only will probably not introduce bugs in many
existing Java programs. But I do think that behavior is more
complicated to formally model and is counter-intuitive.

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