[10] RFR: 8185164: GetOwnedMonitorInfo() returns incorrect owned monitor

[Yasumasa Suenaga]

Hi,

> I think the fix is sound and prevents anyone from observing the case where the monitor will be seen in the stack-frame, but has not yet been set as the "pending monitor". As far as I can tell it is only this case (GetOwnedMonitorInfo from the contended-monitor event callback in the current thread) that will be able to observe the change.

Thanks David,

Dan or David, could you check this change on JPRT?


Yasumasa



On 2017/08/01 13:14, David Holmes wrote:
> Hi Dan,
> 
> On 26/07/2017 11:52 PM, Daniel D. Daugherty wrote:
>> On 7/26/17 12:11 AM, David Holmes wrote:
>>> On 26/07/2017 10:27 AM, Yasumasa Suenaga wrote:
>>>> Hi Dan,
>>>>
>>>>> I've added some analysis to the bug report
>>>>
>>>> Thanks!
>>>> I tried to fix this issue in JvmtiEnvBase::get_owned_monitors() at first.
>>>> But it is difficult because we cannot know pending monitor if thread state is MONITOR_CONTENDED_ENTER when get_owned_monitor() is called.
>>>
>>> I need to look closer at this when I get back from vacation next week.
>>
>> Seems like you're back already. :-)
>>
>>
>>> A pending monitor should not be reported as owned (unless the spec says otherwise) and it seems odd to me to fix the current problem by marking the monitor as pending earlier.
>>
>> It's the updating of the _current_pending_monitor field that
>> allows JvmtiEnvBase::get_locked_objects_in_frame() to recognize
>> that the monitor observed in the frame is only pending and
>> is not owned.
>>
>> I put a fairly detailed note in the bug yesterday, but you
>> should look at that when you're officially back!
> 
> Thanks for clarifying things. I also added a comment to the bug report.
> 
> I think the fix is sound and prevents anyone from observing the case where the monitor will be seen in the stack-frame, but has not yet been set as the "pending monitor". As far as I can tell it is only this case (GetOwnedMonitorInfo from the contended-monitor event callback in the current thread) that will be able to observe the change.
> 
> Thanks,
> David
> 
>> Dan
>>
>>
>>>
>>> Thanks,
>>> David
>>>
>>>>> Did you run the jdk repo's com/sun/jdi tests with your fix?
>>>>
>>>> I have not done yet.
>>>> I have a trip until 28 July JST. So I will run it after that.
>>>>
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> On 2017/07/26 7:05, Daniel D. Daugherty wrote:
>>>>> On 7/24/17 8:40 PM, Yasumasa Suenaga wrote:
>>>>>> Hi all,
>>>>>>
>>>>>> I tried to get owned monitors in MonitorContendedEnter JVMTI event handler.
>>>>>> However GetOwnedMonitorInfo JVMTI function returns a monitor which is
>>>>>> not yet owned.
>>>>>>
>>>>>> I attached reproducer to JBS. Please read README.md.
>>>>>>
>>>>>> I think GetOwnedMonitorInfo() should not return a pending monitor.
>>>>>>
>>>>>>
>>>>>> I uploaded webrev. Could you review?
>>>>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8185164/webrev.00/
>>>>>>
>>>>>> I hope this fix is applied to 8u or later release.
>>>>>> I cannot access JPRT. So I need a sponsor.
>>>>>
>>>>> Thanks for the bug report. It's nice to have a test case and a proposed
>>>>> fix all in the bug report! I've added some analysis to the bug report
>>>>> and we'll need to run this fix through Oracle's JPDA test stack which
>>>>> is not (yet) open.
>>>>>
>>>>> Did you run the jdk repo's com/sun/jdi tests with your fix?
>>>>>
>>>>> Dan
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Yasumasa
>>>>>
>>