RFR: 8298783: java/lang/ref/FinalizerHistogramTest.java failed with "RuntimeException: MyObject is not found in test output" [v7]

[Kim Barrett]

On Tue, 29 Apr 2025 22:46:22 GMT, Brent Christian <bchristi at openjdk.org> wrote:

>> I propose some cleanups to `FinalizerHistogramTest.java` to hopefully clear up the intermittent failures:
>> 
>> * run with `othervm`: this test blocks the (global) finalizer thread, and also requires the (global) finalizer thread to enter the test's `finalize()` method
>> * The test uses `volatile` ints, but sets them based on their current value, which is not reliable; convert to `AtomicInteger`
>> * use `PhantomReference`s to ensure that at least two `MyObject`s have become unreachable. If one is stuck in `finalize()`, at least one is still waiting to be finalized and should show up in the histogram.
>
> Brent Christian has updated the pull request incrementally with one additional commit since the last revision:
> 
>   convert test to use WhiteBox

Changes requested by kbarrett (Reviewer).

test/jdk/java/lang/ref/FinalizerHistogramTest.java line 77:

> 75:             wb = WhiteBox.getWhiteBox();
> 76:             wb.fullGC();
> 77:             refProResult = wb.waitForReferenceProcessing();

WhiteBox::waitForReferenceProcessing returns true if some progress has been made, not if all the 
processing is done.  Probably need a loop here, e.g.

while (wb.waitForReferenceProcessing()) {}
// All finalizable objects from prior gcs have made it to the finalizer queue.

test/jdk/java/lang/ref/FinalizerHistogramTest.java line 79:

> 77:             refProResult = wb.waitForReferenceProcessing();
> 78:             System.out.println("waitForReferenceProcessing returned: " + refProResult);
> 79:             while(trappedCount.get() < 1);

This doesn't seem to be doing anything?  trappedCount is initially 0, and only incremented.

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PR Review: https://git.openjdk.org/jdk/pull/24143#pullrequestreview-2805296214
PR Review Comment: https://git.openjdk.org/jdk/pull/24143#discussion_r2067567008
PR Review Comment: https://git.openjdk.org/jdk/pull/24143#discussion_r2067567096