Re: [rvm-research] Bug in Classpath's VMProcess w.r.t. use of notify() instead of notifyAll()

On 25 April 2013 17:50, Carl Ritson <[email protected]> wrote:
> Hi,
>
> I've been chasing a bug which causes benchmarks from Dacapo 2006 to
> hang with the concurrent collector we are implementing.  I've tracked
> the source of the bug to VMProcess in Classpath.  VMProcess performs a
> notify() on state changes rather than notifyAll(), this means that if
> one thread calls waitFor() on a Process object waiting for its
> termination and another calls destroy() then only one of the two will
> be woken up.
>
> This occurs during stress testing with Dacapo 2006's Eclipse benchmark
> which calls external commands with a timeout.  Under high load the
> external processes do not finish within the timeout period and
> destroy() is called.  At the same time Eclipse's process monitor
> thread is waiting in waitFor().  Only the waitFor() thread detects
> termination, the destroy() thread is never resumed.
>
> The attached program can reproduce the bug in miniature with any
> version of Jikes compiled against Classpath.  This can be fixed by
> applying the attached patch to classpath any version.
>
> Cheers,
>
> Carl
>
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Sorry, I remember reading about this issue before and thought we'd
fixed it.  There
are very few situations where notify() is appropriate.  I know I've
never used it in my
own code.

I'll get this fix into Classpath git as soon as I can.

Thanks,
--
Andii :-)

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