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From "Weldon Washburn" <weldon...@gmail.com>
Subject Re: [testing] Reliability test suite is contributed, HARMONY-2918
Date Mon, 01 Jan 2007 01:11:54 GMT
On 12/28/06, Oleg Oleinik <oleg.oleinik@gmail.com> wrote:
> Hi,
> Reliability test suite is contributed on behalf of Intel:
> http://issues.apache.org/jira/browse/HARMONY-2918
> The tests are intended to verify ability of the runtime to run
> successfully for long time. The suite contains 72 tests (covering
> mainly kernel, nio, text, io, net, zip classes functionality, plus a
> couple of tests for VM) and ant scripts to build and run tests.
> The tests are intented to be integrated into buildtest/. Please review
> and comment.

This is great.  These are much needed tests.

I have started looking at the tests and have questions about

regionIn() corresponds to the part of the Dekker algorithm that acquires the
critical section.  regionIn() contains code that, as far as I can tell, is
not part of the Dekker algorithm.  regionIn() spins for 100000 loops then
assumes/pretends the critical section has been acquired (??).  The line of
code I refer to is:

while (current != worker && k < 100000) {k++;}

>From reading the Dekker algo reference, it seems this line of code probably
should be:

while (current != worker) { }

The burning question is why was the "k < 100000" test added?

At the top of DekkerTest.java it says, "Goal: check that VM supports
volatile variables".  My guess is that the JIT must put memory fence(s)
around volatile variable reads and writes.  My guess is that Dekker is
probably one of the few ways to actually test for proper implementation.
But I really worry that the JIT could accidentally miss emitting the memory
fence(s).  And DekkerTest.java would pass anyway.  Does it make sense to
create "DekkerTest2.java" that is identical to DekkerTest.java where all the
"volatile" kepwords are omitted?  The intention is to create a test that
will hard fail if the memory fences are not emitted.

Best regards, Oleg

Weldon Washburn
Intel Enterprise Solutions Software Division

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