RFR: 8286294 : ForkJoinPool.commonPool().close() spins [v4]

[Martin Buchholz]

On Sat, 7 May 2022 11:29:32 GMT, Doug Lea <dl at openjdk.org> wrote:

>> Changes ForkJoinPool.close spec and code to trap close as a no-op if called on common pool
>
> Doug Lea has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Accommodate restrictive SecurityManagers
>  - merge with loom updates
>    Merge remote-tracking branch 'refs/remotes/origin/JDK-8286294' into JDK-8286294
>  - Fix testLazySubmit; enable suite

Here's a suggested strengthening of testCloseCommonPool:

- close should have "no effect", not just "not terminate".
- the submitted task will be run by the pool ... eventually  (which suggests that closing the common pool maybe should quiesce the pool before returning)
-  I might merge this with testCommonPoolShutDown

    /**
     * Implicitly closing common pool using try-with-resources has no effect.
     */
    public void testCloseCommonPool() {
        ForkJoinTask f = new FibAction(8);
        ForkJoinPool pool;
        try (ForkJoinPool p = pool = ForkJoinPool.commonPool()) {
            p.execute(f);
        }

        assertFalse(pool.isShutdown());
        assertFalse(pool.isTerminating());
        assertFalse(pool.isTerminated());

        String prop = System.getProperty(
            "java.util.concurrent.ForkJoinPool.common.parallelism");
        if (! "0".equals(prop)) {
            f.join();
            checkCompletedNormally(f);
        }
    }

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

PR: https://git.openjdk.java.net/jdk/pull/8577