ThreadPoolExecutor#kill will wait_for_termination in JRuby; ensure TimerSet timer thread shuts down cleanly#1044
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eregon merged 1 commit intoruby-concurrency:masterfrom Dec 11, 2025
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kill will wait_for_termination in JRubykill should wait_for_termination in JRuby
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kill should wait_for_termination in JRubykill should wait_for_termination in JRuby to be consistent with Ruby
…e TimerSet timer thread shuts down cleanly
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kill should wait_for_termination in JRuby to be consistent with RubyThreadPoolExecutor#kill will wait_for_termination in JRuby; ensure TimerSet timer thread shuts down cleanly
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ThreadPoolExecutor#kill will wait_for_termination in JRuby; ensure TimerSet timer thread shuts down cleanlyThreadPoolExecutor#kill will wait_for_termination in JRuby; ensure TimerSet timer thread shuts down cleanly
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This fixes an inconsistency in behavior in ThreadPoolExecutor in Ruby and JRuby.
Extracted from #1042, explained in #1041.
Changing the behavior of
killto wait until all threads exited exposed a problem withTimerSet's timer thread. It was not previously being completely shut down. The change was to ensure that the loopedEvent.waitis released withEvent#seton shutdown.One wrinkle in TimerSet is that shutdown is wrapped with a mutex that also is locked in the timer thread, which could lead to a deadlock: shutdown takes mutex and waits for timer thread to exit; meanwhile the timer thread is itself trying to acquire the mutex in order to execute through and exit... therefore deadlock. My solution to this was moving the timer thread's kill / await-thread-termination outside of the mutex.
This deadlock was largely masked because JRuby wasn't waiting on the threads to exit (changed in this PR) whereas CRuby would simply kill the threads so they would have a chance to deadlock on the mutex.