RFR [8038333] java/lang/ref/EarlyTimeout.java failed

[David Holmes]

Ivan,

I think the problem is that the EarlyTimeout threads can complete their 
remove(TIMEOUT) before the main thread has started them all, cleared the 
reference and called System.gc().

Depending on exactly what is being tested, the EarlyTimeout threads may 
need to wait on another latch that is signalled by the main thread after 
the gc() call returns. Still no guarantee that the gc will do its work 
before the timeout elapses.

David

On 27/03/2014 6:18 AM, Ivan Gerasimov wrote:
> Thank you Mandy!
>
>> Are you able to reproduce the test failure?
>
> Yes, I could easily reproduce the failure when I reduced the timeout to
> 10 ms.
> With the timeout reduced, the test fails every third time on my machine.
>
>> I think the test verifies that only one thread gets the reference is a
>> good test.
>>
> But if none of the threads could get the reference, it should not cause
> the failure of the test.
> It only means that during this particular run we could not have tested
> what we needed.
> We could retry, but I'm not sure it's worth complicating the test.
> It's easier to ignore the failure, taking into account that it happens
> rarely.
>
>> I think the race is due to the threads get to call queue.remove as
>> soon as both threads decrement the count of the latch that can be well
>> before the reference is enqueued.
>>
> The problem is that we have no way to block the main thread until there
> is a reference in the queue.
> I improved the situation a bit, having moved the await() after the call
> of gc().
>
>> It'd be good to add additional information in the test to help
>> diagnosing test failure.
>>
> I added reporting to stderr about being unable to remove a reference
> from the queue.
> I believe we shouldn't treat it as an error, and should simply ignore it.
>
> Would you please have a look at the updated webrev:
> http://cr.openjdk.java.net/~igerasim/8038333/1/webrev/
>
> Sincerely yours,
> Ivan
>
>