RFR: 8300727: java/awt/List/ListGarbageCollectionTest/AwtListGarbageCollectionTest.java failed with "List wasn't garbage collected"

[Alexey Ivanov]

On Thu, 16 Feb 2023 21:41:12 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> The test has become unstable recently, there were quite a few failures, on Windows mostly. I was lucky enough to find a host where the test failed consistently.
>> 
>> I call `System.gc()` directly as suggested in comments to the bug. I used `PhantomReference` instead of `WeakReference`.
>> 
>> Now the test calls `System.gc()` in a loop and waits for the reference to be enqueued. In majority of cases, the test exits the loop at the second attempt.
>
> test/jdk/java/awt/List/ListGarbageCollectionTest/AwtListGarbageCollectionTest.java line 72:
> 
>> 70:         do {
>> 71:             System.out.println("Attempt " + count);
>> 72:             System.gc();
> 
> As far as I remember the call of System.gc() could be ignored, and the only way to trigger GC is to trigger the OOM. Probably we can combine referenceQueue.remove(ENQUEUE_TIMEOUT) + OOM?

For this reason, GC logs are enabled. If, for whatever reason, the call to `System.gc()` is ignored, we'll see it in the test log. Then a specific GC could be selected, for example, or another fix implemented.

OOME does not guarantee a full GC cycle either.

Having the above in mind, I'd rather keep it simple.

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PR: https://git.openjdk.org/jdk/pull/12594