I've had the testsuit hang frequently recently and it seems this stack is often found in such cases:

> "pool-3-thread-14" prio=10 tid=0x00007f0d84632000 nid=0x1ce5 runnable
> [0x00007f0d58a36000]
> java.lang.Thread.State: RUNNABLE
> at java.util.HashMap.put(HashMap.java:374)
> at org.testng.SuiteRunner.runTest(SuiteRunner.java:320)
> at org.testng.SuiteRunner.access$000(SuiteRunner.java:34)
> at org.testng.SuiteRunner$SuiteWorker.run(SuiteRunner.java:351)
> at org.testng.internal.thread.ThreadUtil$CountDownLatchedRunnable.run(ThreadUtil.java:147)
> at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)

If after a while I take another thread dump, the thread is still looping around at the same line.
I couldn't reproduce the problem with TestNG 6.7, not sure if they solved it or if it's just less likely.