RFR [7181748] TEST_BUG: java/lang/ThreadGroup/Suspend test fails intermittently

[Ivan Gerasimov]

Thank you, David.

I've reverted the code back, added volatile specification to the count 
variable.
Would you please review the webrev with this only change (comparing to 
webrev.0):
http://cr.openjdk.java.net/~igerasim/7181748/webrev.2/

Sincerely yours,
Ivan

On 12.06.2013 13:49, David Holmes wrote:
> On 12/06/2013 12:13 AM, Ivan Gerasimov wrote:
>> Chris and David, thanks for review.
>>
>> I've updated the test so the threads use CountDownLatch to wait for each
>> other.
>> Now, instead of checking whether the 'second' thread has incremented a
>> count, the 'main' thread waits for it to call countDown().
>> If a timeout was elapsed before the call, I assume that the 'second'
>> thread is suspended and the test passes.
>
> I do not advise doing this. The second thread can be suspended inside 
> the CountdownLatch code. When suspend is involved you do not want any 
> direct interaction between the main thread and the thread being 
> suspended.
>
> David
> -----
>
>> Could you please review the updated webrev:
>> http://cr.openjdk.java.net/~igerasim/7181748/webrev.1/
>>
>> Sincerely,
>> Ivan
>>
>> On 11.06.2013 13:37, Chris Hegarty wrote:
>>> On 06/11/2013 08:08 AM, David Holmes wrote:
>>>> On 11/06/2013 1:54 AM, Chris Hegarty wrote:
>>>>> I'm not sure I ever saw this test fail, but it does look like it has
>>>>> issues.
>>>>>
>>>>> I would much prefer to see a j.u.c.Latch/Phaser used to synchronize
>>>>> across these threads.
>>>>
>>>> I don't think that is possible. The main thread wants to reset the 
>>>> count
>>>> after the suspend has been issued by "first", but once the suspend has
>>>> been issued the "first" thread can't signal the synchronizer to let 
>>>> the
>>>> main thread proceed. The poll around isAlive() does address the main
>>>> issue of a slowly starting thread.
>>>
>>> Ah yes, thanks David. In which case I'm fine with the change.
>>>
>>>> For completeness the count variable should be volatile as well.
>>>
>>> Agreed.
>>>
>>> -Chris.
>>>
>>>>
>>>> Cheers,
>>>> David
>>>>
>>>>> -Chris.
>>>>>
>>>>> On 10/06/2013 13:51, Ivan Gerasimov wrote:
>>>>>> Hello everyone!
>>>>>>
>>>>>> The test of ThreadGroup.Suspend() was reported to fail on rare
>>>>>> occasions.
>>>>>> It can happen on a busy machine that 1 second delay would not be
>>>>>> enough
>>>>>> for the second thread to start.
>>>>>> Then the first thread would suspend only itself and the test would
>>>>>> fail.
>>>>>> Earlier, another test was updated for similar reasons [1], [2].
>>>>>>
>>>>>> The proposed test can still report false *positive* results if the
>>>>>> second thread has had no chance to execute during one second 
>>>>>> after it
>>>>>> had started.
>>>>>> To avoid them there must be a way do distinguish suspended threads.
>>>>>>
>>>>>> WEBREV: http://cr.openjdk.java.net/~igerasim/7181748/webrev.0/
>>>>>> BUG: http://bugs.sun.com/view_bug.do?bug_id=7181748
>>>>>>
>>>>>>
>>>>>> [1] http://bugs.sun.com/view_bug.do?bug_id=7084033
>>>>>> [2] http://hg.openjdk.java.net/jdk8/jdk8/jdk/rev/184578f3e8b9
>>>>>>
>>>>>> Sincerely yours,
>>>>>> Ivan Gerasimov
>>>>>> <https://jbs.oracle.com/bugs/browse/JDK-7084033>
>>>
>>>
>>
>
>