RFR 8071641: java/lang/management/ThreadMXBean/SynchronizationStatistics.java intermittently failed with NPE

[shanliang]

Jaroslav Bachorik wrote:
> Please, review the following test change.
>
> Issue : https://bugs.openjdk.java.net/browse/JDK-8071641
> Webrev: http://cr.openjdk.java.net/~jbachorik/8071641/webrev.00/
>
> The test fails very intermittently with NPE. This seems to be caused 
> by a data race between Thread.getStatus() and 
> ThreadMXBean.getThreadInfo() - thread state is reported as BLOCKED but 
> the ThreadInfo still contains a stale information (lockname == null).
>
> The solution would be re-retrieving the ThreadInfo until it reflects 
> the actual thread state.
>
> -JB-
  77     private static void waitForThreadState(Thread t, Thread.State 
state) throws InterruptedException {
  78         while (!t.isInterrupted() && t.getState() != state) {
  79             Thread.sleep(3);
  80         }
  81     }
Better to throw an exception if t.isInterrupted()?
Not sure when will happen t.isInterrupted(), but the method 
waitForThreadState tests it, so it is supposed to be possible to get it, 
when it is true then the testing method might return with a thread state 
different to the waited one.

Shanliang