RFR 6712222: 6712222: Race condition in java/lang/management/ThreadMXBean/AllThreadIds.java

[Jaroslav Bachorik]

Please, review the following test change

Issue : https://bugs.openjdk.java.net/browse/JDK-6712222
Webrev: http://cr.openjdk.java.net/~jbachorik/6712222/webrev.00

As the issue subject states this test is susceptible to race condition. 
Firstly, it uses an arbitrary time period to wait after a thread has 
signalled its exit vie the associated barrier to 'make sure' the thread 
is actually terminated when the check for the number of live threads is 
performed. This is quite race prone and should be replaces by 
Thread.join() performed on the specified threads before moving forward 
and checking the reported thread counts.

Secondly, it is using a volatile array of boolean flags which are used 
for communication between the main thread and the test threads (setting 
an item of this array true will indicate the appropriate test thread to 
exit). Declaring the array as volatile does nothing for the thread 
safety and reads and writes to this array must be properly synchronized.

I also took the liberty of replacing the arbitrary Barrier 
synchronization class with the standard Semaphore.


Thanks,

-JB-