Patch review request - Test bug 7123972 test/java/lang/annotation/loaderLeak/ fails intermittently

Eric Wang at
Thu Jun 28 06:23:01 UTC 2012

Hi Stuart,

Thank you for help to publish the fix, my pleasure to contribute to 
OpenJDK project.


On 2012/6/28 12:40, Stuart Marks wrote:
> I've posted the webrev here:
> I've looked at the changes and they seem fine.
> It's interesting that the run times take 30-60 sec in your experience. 
> I've run them on my system (Linux in a virtual machine) and they 
> usually run in 10-20 sec. In any case, as you say, if the test times 
> out it indicates there really was a failure.
> I'll give people a chance to look at the webrev and if there aren't 
> any more comments in another day or so I'll push in the changeset.
> Thanks for developing this!
> s'marks
> On 6/26/12 11:50 PM, Eric Wang wrote:
>> Hi David,
>> Thank you! I run the test several times on 3 platforms (windows, 
>> solaris and
>> linux), the average execution time is 30secs to 60secs. if the test 
>> hang 2
>> minutes, there should be something wrong.
>> Hi Marks,
>> I don't have the author role, Can you please help to review and post 
>> the webrev
>> in attachment if it is OK, Thanks a lot!
>> Regards,
>> Eric
>> On 2012/6/27 14:19, David Holmes wrote:
>>> Eric,
>>> Ignore my comment about adding the timeouts. As Alan reminded me if 
>>> the test
>>> would hang then jtreg will time it out after two minutes anyway.
>>> So this is good to go as far as I am concerned.
>>> Thanks,
>>> David
>>> On 27/06/2012 7:51 AM, David Holmes wrote:
>>>> Thanks Eric.
>>>> So to summarize:
>>>> - we create a custom classloader, load a class through it and store a
>>>> reference to that Class in a WeakReference
>>>> - we then drop the reference to the loader
>>>> At this point the only reference to the loader is from the Class 
>>>> loaded,
>>>> which in turn is only weakly reachable.
>>>> I must confess that I'm unclear why this test should be failing in its
>>>> original form. The first gc() should remove the strong reference to 
>>>> the
>>>> loader. That leaves a weak cycle: WeakRef -> Class -> Loader -> Class.
>>>> The second gc() should detect the cycle and clear the WeakRef. I guess
>>>> the problem is that depending on which gc is in use the actual gc()
>>>> calls may not in fact induce every possible GC action.
>>>> The fix seems reasonable in that regard - keep gc'ing and finalizing
>>>> till we see the loader is gone, and so the WeakReference should be
>>>> cleared. The original bug would cause a ref to the Class to remain 
>>>> (from
>>>> the annotation) and hence the WeakRef would not be cleared. 
>>>> However, in
>>>> that case the loader would also be strongly referenced and so never
>>>> become finalizable. So if this test was now run against a JDK with the
>>>> original bug, the test would hang. So I think we need to add a timeout
>>>> in there as well.
>>>> David
>>>> On 25/06/2012 6:06 PM, Eric Wang wrote:
>>>>> On 2012/6/21 20:16, David Holmes wrote:
>>>>>> Hi Eric,
>>>>>> On 21/06/2012 8:57 PM, Eric Wang wrote:
>>>>>>> Hi David,
>>>>>>> Thanks for your review, I have updated the code by following your
>>>>>>> suggestion. please see the attachment.
>>>>>>> I'm not sure whether there's a better way to guarantee object 
>>>>>>> finalized
>>>>>>> by GC definitely within the given time. The proposed fix may 
>>>>>>> work in
>>>>>>> most cases but may still throw InterruptException if execution is
>>>>>>> timeout (2 minutes of JTreg by default).
>>>>>> There is no way to guarantee finalization in a specific 
>>>>>> timeframe, but
>>>>>> if a simple test hasn't executed finalizers in 2 minutes then 
>>>>>> that in
>>>>>> itself indicates a problem.
>>>>>> Can you post a full webrev for this patch? I don't like seeing it 
>>>>>> out
>>>>>> of context and am wondering exactly what we are trying to GC here.
>>>>>> David
>>>>>>> Regards,
>>>>>>> Eric
>>>>>>> On 2012/6/21 14:32, David Holmes wrote:
>>>>>>>> Hi Eric,
>>>>>>>> On 21/06/2012 4:05 PM, Eric Wang wrote:
>>>>>>>>> I come from Java SQE team who are interested in regression 
>>>>>>>>> test bug
>>>>>>>>> fix.
>>>>>>>>> Here is the first simple fix for bug 7123972
>>>>>>>>> <>, Can you 
>>>>>>>>> please
>>>>>>>>> help
>>>>>>>>> to review and comment? Attachment is the patch Thanks!
>>>>>>>>> This bug is caused by wrong assumption that the GC is started
>>>>>>>>> immediately to recycle un-referenced objects after System.gc() 
>>>>>>>>> called
>>>>>>>>> one or two times.
>>>>>>>>> The proposed solution is to make sure the un-referenced object is
>>>>>>>>> recycled by GC before checking if the reference is null.
>>>>>>>> Your patch makes its own assumptions - specifically that 
>>>>>>>> finalization
>>>>>>>> must eventually run. At a minimum you should add
>>>>>>>> System.runFinalization() calls after the System.gc() inside the 
>>>>>>>> loop.
>>>>>>>> Even that is no guarantee in a general sense, though it should 
>>>>>>>> work
>>>>>>>> for hotspot.
>>>>>>>> David
>>>>>>>>> Regards,
>>>>>>>>> Eric
>>>>> Hi Alan & David,
>>>>> Thank you for your comments, sorry for reply this mail late as i was
>>>>> just back from the dragon boat holiday.
>>>>> I have updated the code again based on your suggestions: rename 
>>>>> the flag
>>>>> variable, increase the sleep time and remove it from problem list.
>>>>> The attachment is the full webrev for this patch, Can you please 
>>>>> review
>>>>> again? Thanks a lot!
>>>>> Regards,
>>>>> Eric

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