RFR: 8302899: Executors.newSingleThreadExecutor can use Cleaner to shutdown executor

[Alan Bateman]

On Tue, 21 Feb 2023 15:45:17 GMT, Viktor Klang <duke at openjdk.org> wrote:

>> Executors.newSingleThreadExecutor returns a delegating ExecutorService that has finalizer to shutdown the underlying TPE when the wrapper is finalizable. It goes back to JDK 6 and JDK-6399443. This is the last non-empty finalizer in java.base. Removing it will likely lead to bug reports/complaints as the current behavior goes back to 2006. So the proposal is to just replace it with a Cleaner, trivially done in this case. As part of the changes, I've replaced the existing test with a more modern test that exercises more scenarios.
>
> test/jdk/java/util/concurrent/Executors/AutoShutdown.java line 133:
> 
>> 131:         while (!terminated) {
>> 132:             System.gc();
>> 133:             terminated = executor.awaitTermination(100, TimeUnit.MILLISECONDS);
> 
> @AlanBateman Perhaps worth having some upper limit as to how long it will wait until failing the test?

jtreg will look after this. The default timeout is 120s but it can be adjusted with a timeout factor (make time uses a timeout factor of 4). So it would be possible to put a limit on this in the test but it can be problematic, e.g. with debug builds + Xcomp for example.

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PR: https://git.openjdk.org/jdk/pull/12675