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

[Daniel D.Daugherty]

On Wed, 15 Dec 2021 02:34:40 GMT, David Holmes <dholmes 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 ???

See L71 below:   _ptrs->unlink(&cleanup);  // cleanup the LinkedLists
That passes the cleanup object to ResourceHashtable::unlink()
function which calls the do_entry() function in the cleanup object.

-------------

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