[10] RFR for JDK-8169961: Memory leak after debugging session

[serguei.spitsyn at oracle.com]

On 8/9/17 08:27, Daniel D. Daugherty wrote:
> On 8/9/17 3:05 AM, Shafi Ahmad wrote:
>> May I get it reviewed by  serviceability team.
>
> I don't count as being on the Serviceability team anymore, but

Common, Dan, you are still counted! :)

> I've pinged Serguei Spitsyn who is back from his vacation...
>
> More below...

More below.

>
>
>>
>> Regards,
>> Shafi
>>
>>
>>
>>> -----Original Message-----
>>> From: Shafi Ahmad
>>> Sent: Wednesday, July 26, 2017 8:26 AM
>>> To: serviceability-dev at openjdk.java.net
>>> Cc: Roger Calnan <roger.calnan at oracle.com>
>>> Subject: RE: [10] RFR for JDK-8169961: Memory leak after debugging 
>>> session
>>>
>>> May I get it reviewed by someone from serviceability group.
>>>
>>> Webrev link: http://cr.openjdk.java.net/~shshahma/8169961/webrev.01/
>>> This review thread: 
>>> http://mail.openjdk.java.net/pipermail/serviceability-
>>> dev/2017-July/021538.html
>>>
>>> Regards,
>>> Shafi
>>>
>>>> -----Original Message-----
>>>> From: Shafi Ahmad
>>>> Sent: Monday, July 24, 2017 12:52 PM
>>>> To: serviceability-dev at openjdk.java.net
>>>> Subject: RE: [10] RFR for JDK-8169961: Memory leak after debugging
>>>> session
>>>>
>>>> Hi,
>>>>
>>>>> -----Original Message-----
>>>>> From: Langer, Christoph [mailto:christoph.langer at sap.com]
>>>>> Sent: Monday, July 17, 2017 9:01 PM
>>>>> To: Poonam Parhar <poonam.bajaj at oracle.com>
>>>>> Cc: Shafi Ahmad <shafi.s.ahmad at oracle.com>; serviceability-
>>>>> dev at openjdk.java.net
>>>>> Subject: RE: [10] RFR for JDK-8169961: Memory leak after debugging
>>>>> session
>>>>>
>>>>> Hi Poonam,
>>>>>
>>>>>
>>>>>> Line 182: Here, eventController.release() is called after the 'vm'
>>>>>> is
>>>> disposed.
>>>>>> And eventController.release() causes the following statement to be
>>>>>> executed on the eventcontroller thread after the 'vm' is disposed:
>>>>>>
>>>>>> JDWP.VirtualMachine.ReleaseEvents.process(vm);
>>>>>>
>>>>>> Which does not seem to be right. Someone from the Serviceability
>>>>>> group can confirm the correctness of this change.
>>>>> I think this is okay, because with the new change shouldListen() is
>>>>> called right after the thread returns from wait(). And this will
>>>>> lead to the thread immediately exiting.
>>>>> JDWP.VirtualMachine.ReleaseEvents.process(vm);
>>>>> should not be called in this case.
>
> I just re-read the webrev and I agree with Christoph that this new check:
>
>   L358:                         if (!shouldListen) {
>   L359:                            return;
>   L360:                         }
>
> will keep the EventController.run() method from trying to
> use the 'vm' that has been disposed.

Agreed.
The only issue is that the 'shouldListen' field has to be volatile now.

Otherwise, the fix looks good to me.

Thank you for taking care about this issue!

Thanks,
Serguei

>
> Dan
>
>
>>>>>
>>>>>> Line 330: Instance variable 'VirtualMachineImpl vm' is removed
>>>>>> from the EventController class. It is being used further down in
>>>>>> its
>>>>>> run() method. So I think it cannot be removed.
>>>>> The vm object is used from the outer class TargetVM, as
>>>>> EventController is an inner class of it.
>>>>>
>>>>> So in my view it's all correct but still somebody of the
>>>>> serviceability group might know better...
>>>> Could someone from serviceability group review this.
>>>>
>>>> Regards,
>>>> Shafi
>>>>
>>>>> Best regards
>>>>> Christoph
>>>>>
>