RFR: 8066952 [TEST-BUG] javax/management/monitor/CounterMonitorTest.java hangs

[shanliang]

Hi,

As Daniel said: "I think that what happens here is that the 
StdObservedObject.getNbObjects() getter unblocks the main thread before 
returning the value to the monitor. This makes it possible to have a 
race condition where the next setNbObjects called by the main thread can 
then occur before the result of StdObservedObject.getNbObjects() is 
taken into account - and even before the 
StdObservedObject.getNbObjects() actually returns. So 
StdObservedObject.getNbObjects() may return a value different than the 
one which was observed. In our case, it would return 3 (the newer value) 
instead of 0 (the value that was observed). "

The suggested fix is to return "observedValue" instead of "count", in 
this way we check also that the monitor never starts next observation 
before the current one finishes.

bug: https://bugs.openjdk.java.net/browse/JDK-8066952
webrev: http://cr.openjdk.java.net/~sjiang/JDK-8066952/00/

Thanks,
Shanliang