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From Gregory Shimansky <gshiman...@gmail.com>
Subject Re: [drlvm][reliability tests] Harmony-2986, Dekker's algorithm -- is this a valid test for modern SMP hardware?
Date Thu, 22 Feb 2007 00:03:47 GMT
On Wednesday 21 February 2007 21:47 Rana Dasgupta wrote:
> Weldon,
>   But I am not sure why the behavior would be different from J9 on the same
> hardware. Do we jit volatiles differently?

There is a bug on DRLVM about volatile variables HARMONY-2092. It is about 
long and double type variables assignments. Is it the same as in Dekker's 
algorithm?

> On 2/20/07, Weldon Washburn <weldonwjw@gmail.com> wrote:
> > It seems Dekker's algorithm is not expected to work on SPARC or IA32 SMP
> > boxes unless memory fences are used.  DekkerTest.java in Harmony-2986
> > does not contain memory fences.  The volatile keyword guarantees the
> > compiler will write a given variable to memory.  However, the HW may
> > actually have a
> > write buffer and allow reads to pass writes.  As far as I know, the Java
> > language does not provide a means to invoke a memory fence.  Thus there
> > is no way to fix up DekkerTest.java.  I may be misunderstanding something
> > here.  Does anyone have comment?
> >
> > An excellent description of the issues involved is in a David Dice
> > presentation at:
> >
> > http://blogs.sun.com/dave/resource/synchronization-public2.pdf
> >
> > --
> > Weldon Washburn
> > Intel Enterprise Solutions Software Division

-- 
Gregory

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