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

[David Holmes]

On Tue, 14 Dec 2021 21:16:02 GMT, Daniel D. Daugherty <dcubed 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.

src/hotspot/share/runtime/synchronizer.cpp line 62:

> 60: class CleanupObjectMonitorsHashtable: StackObj {
> 61:  public:
> 62:   bool do_entry(JavaThread*& key, ObjectMonitorsHashtable::PtrList*& list) {

I don't see this being called by anything ???

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