jmx-dev RFR: 8020875 java/lang/management/ThreadMXBean/ResetPeakThreadCount.java fails intermittently

[Chris Hegarty]

On 24/07/2013 12:21, David Holmes wrote:
> On 24/07/2013 7:31 PM, Mandy Chung wrote:
>>
>> On 7/24/2013 4:50 PM, shanliang wrote:
>>> So we have 2 kinds of issues here:
>>> 1) the test related, like Thread state checking, we can fix them in
>>> the test
>>> 2) MBean.getThreadCount() issue, we can create a bug to trace it (add
>>> your test case to the bug), and add a workaround (sleep or call 2
>>> times) in the test to make the test pass. Mandy is the expert and
>>> better to get her opinion.
>>
>> It's probably a race in the VM implementation in determining the thread
>> count. You will need to diagnose the VM implementation and compare the
>> thread list and the implementation of getting the thread count (check
>> hotspot/src/share/vm/services/threadService.cpp)
>
> There is a considerable code path between the point where a terminating
> thread causes Thread.join() to be allowed to return, and the point where
> the live thread count gets decremented. So using join() does not help
> here. Arguably JVMTI should have based its counts around the lifecycle
> of the Java thread not the underlying native thread.

It appears, from my reading of the code, that this situation ( a thread 
exiting ) should be handled. Or maybe I'm looking at the wrong interface.

JavaThread::exit(...) {
   ...
   ThreadService::current_thread_exiting(this);
   ...
   ensure_join(..)
   ...
}

So the exiting thread should be removed from the live thread count 
before Thread.join returns.

-Chris.

>
> David
> -----
>
>> Mandy