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

[Jaroslav Bachorik]

Thanks everyone for taking the time to dig into this issue.

I've done more testing and it turns out that my initial analysis was 
wrong. There are no threads magically appearing and disappearing (it 
was all caused by the monitoring tools I used). It rather seems that 
there is an issue with terminating the test threads - I've added a lot 
of logging to the original test and was able to observe that sometimes 
the new test threads were started before the terminating test threads 
have disappeared.

So I've added more rigorous check for the threads termination - 
checking the thread states instead of just comparing the thread counts. 
By doing this I was able to decrease the chances of failing but it 
still seems that there is some discrepancy between the numbers reported 
by the mbean and eg. the result of Thread.getAllStackTraces(). I am 
logging all the threads reported by Thread.getAllStackTraces() before 
the call to mbean.getThreadCount() and after the call and sometimes it 
just happens that mbean.getThreadCount() reports the thread count which 
is off by 1 in regards to both Thread.getAllStackTraces() calls.

I will try the "thread.join()" suggestion from Daniel.

-JB-