[jdk18] RFR: 8273107: RunThese24H times out with "java.lang.management.ThreadInfo.getLockName()" is null

[Daniel D.Daugherty]

On Tue, 14 Dec 2021 22:52:46 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> RunThese24H sometimes times out with a couple of error msgs:
>> - "java.lang.management.ThreadInfo.getLockName()" is null
>> - ForkJoin common pool thread stuck
>> 
>> The '"java.lang.management.ThreadInfo.getLockName()" is null' error msg was
>> due to RunThese's use of an older JCK test suite which has since been fixed.
>> 
>> The 'ForkJoin common pool thread stuck' failure mode is likely due to a thread
>> spending a lot of time in ObjectSynchronizer::monitors_iterate() due to a
>> VM_ThreadDump::doit() call. I say "likely" because I've never been able to
>> reproduce this failure mode in testing outside of Mach5. With the Mach5
>> sightings, all we have are thread dumps and core files and not a live process.
>> 
>> The VM_ThreadDump::doit() call is trying to gather owned monitor information
>> for all threads in the system. I've seen sightings of this failure mode with > 2000
>> threads. I've also seen passing runs with > 1.7 million monitors on the in-use list.
>> Imagine searching a larger in-use list for > 2000 threads. It just doesn't scale.
>
> This looks good to me.  You solved both the problem of the very long monitor list and the per-thread iteration too. I like it!

@coleenp - Thanks for chiming in on the official review.

@robehn - Thanks for reviewing!

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PR: https://git.openjdk.java.net/jdk18/pull/25