Re: PostgreSQL XAResource & GlassFish 3.1.2.2

We could patch it so that java 5+ didn't see this the driver already builds
different versions

Dave Cramer

dave.cramer(at)credativ(dot)ca
http://www.credativ.ca

On Tue, Feb 12, 2013 at 1:41 PM, Florent Guillaume <fg(at)nuxeo(dot)com> wrote:

> On Tue, Feb 12, 2013 at 7:36 PM, Heikki Linnakangas
> <hlinnakangas(at)vmware(dot)com> wrote:
> > I see. I think there's yet another potential explanation: even if
> glassfish
> > is careful to invoke the end() only after start() has fully finished in
> the
> > other thread, the java memory model does not guarantee that the effects
> of
> > the end() in one thread are visible to the other thread doing the
> start().
> > The update of the PGXAConnection's state-variable might be sitting in the
> > CPU cache of the CPU running the first thread, not yet visible to the
> second
> > thread.
>
> That's the whole point of volatile since Java 5, it enforces a barrier
> and "happens-before" semantics.
>
> > However, I'm not sure if glassfish could guarantee that the start()
> > has really finished before end() is called, without using some operation
> > that would also force the CPU cache to be flushed, making the effects
> > visible.
> >
> > In any case, it seems like we should add "synchronized" to all the public
> > methods in PGXAConnection. The performance penalty should be minimal,
> and it
> > would fix any race conditions of that sort.
>
> For Java 5+ this is really overkill.
>
> Florent
>
> >
> > Can you test the attached patch?
> >
> > - Heikki
> >
> >
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>
>
>
> --
> Florent Guillaume, Director of R&D, Nuxeo
> Open Source, Java EE based, Enterprise Content Management (ECM)
> http://www.nuxeo.com http://www.nuxeo.org +33 1 40 33 79 87
>
>
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