RFR: 8303916: ThreadLists.java inconsistent results

[Alan Bateman]

On Wed, 14 Jun 2023 09:30:49 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

> This test fails when additional threads are created, as it compares thread lists from different sources and sees a mismatch.
> 
> It needs to tolerate some threads with certain names appearing, e.g. JVMCI and ForkJoin threads.  If there are extra threads in the thread ID list from the ThreadMBean, remove them from the thread count before comparing.
> 
> When it fails, additionally print the ids and names of threads that it got from the MBean.
> 
> I found the test quite confusing, the naming of thread counts, arrays of threads, and arrays of thread stacktraces from different sources, so have renamed some things.

I agree with David and would be concerned this test will be whack-a-mole to deal with other cases. It would be a lot simpler to have a test that creates a number of threads, then uses Thread.getAllThreadStacks + ThreadMXBean.getAllThreadIds to that the expected list of threads are included. If the current thread is not a virtual thread then it can check that it is included too. If you really want to check that both methods return the same list of threads then I think it will need to loop + backoff when the threads aren't the same.

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PR Comment: https://git.openjdk.org/jdk/pull/14465#issuecomment-1592424397