[jira] [Created] (LUCENE-9661) Another classloader deadlock?

["Michael McCandless (Jira)" <ji...@apache.org>]

Michael McCandless created LUCENE-9661:
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             Summary: Another classloader deadlock?
                 Key: LUCENE-9661
                 URL: https://issues.apache.org/jira/browse/LUCENE-9661
             Project: Lucene - Core
          Issue Type: Bug
    Affects Versions: master (9.0)
            Reporter: Michael McCandless


The {{java}} processes spawned by our Lucene nightly benchmarks sometimes randomly hang, apparently while loading classes across threads, under contention.

I've opened [this {{luceneutil}} issue with some details|https://github.com/mikemccand/luceneutil/issues/89], but [~uschindler] suggested I open an issue here too since he has been seeing this in CI builds too.

It is rare, maybe once a week in the nightly benchmarks (which spawn many {{java}} processes with many threads across 128 CPU cores).  It is clearly a deadlock – when it strikes, the process hangs forever until I notice and {{kill -9}} it.  I posted a coupled {{jstacks}} in the issue above.

[~rcmuir] suggested using {{classcycle}} to maybe statically dig into possible deadlocks ... I have not tried that yet.



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