[9] RFR(S): 8054402: "klass->is_loader_alive(_is_alive)) failed: must be alive" for anonymous classes

[Vladimir Kozlov]

Nice work, Tobias!
Should you also modify Dictionary::do_unloading() since it is the only place where it is called and the result is not 
used anymore?
I don't think you need IgnoreUnrecognizedVMOptions flag in the test.

Thanks,
Vladimir

On 8/12/14 2:20 AM, Tobias Hartmann wrote:
> Hi,
>
> please review the following patch that fixes JDK-8054402.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8054402
> Webrev: http://cr.openjdk.java.net/~thartmann/8054402/webrev.00/
>
> == Problem ==
> The test [1] rarely fails with the assert 'klass->is_loader_alive(_is_alive)) failed: must be alive' in
> 'CheckClass::check_class' (nmethod.cpp) because a IC in a compiled method [2] references an unloaded anonymous Klass*
> [3] (i.e., the Klass has an unloaded mirror class [4]). Usually, ICs are cleaned in 'nmethod::do_unloading' by
> 'clean_ic_if_metadata_is_dead' if they reference stale metadata. In this case, the check for stale metadata is not
> performed because 'unloading_occurred' is set to false and therefore no class unloading should have happened.
> The error is in 'SystemDictionary::do_unloading'. First, 'ClassLoaderDataGraph::do_unloading ' is invoked to remove the
> class loader data of unloaded classes. Next, 'Dictionary::do_unloading' is called to remove the system dictionary
> entries of dead classes. 'unloading_occurred' is only set to true if dead class loaders were found _and_ entries were
> removed from the system dictionary. The problem is that anonymous classes are not in the system dictionary. In the rare
> case where only anonymous classes were unloaded, 'unloading_occurred' is set to false even if (anonymous) class
> unloading occurred.
>
> == Solution ==
> The variable 'unloading_occurred' is always set to true if dead class loaders were found.
> I was able to write a jtreg test that deterministically triggers the bug.
>
> == Testing ==
> - New jtreg test
> - Failing test [1]
> - JPRT
>
> Thanks,
> Tobias
>
>
> [1] java/util/stream/test/org/openjdk/tests/java/util/stream/InfiniteStreamWithLimitOpTest.java
> [2] java.util.stream.Streams$RangeIntSpliterator::forEachRemaining
> [3] java.util.stream.StreamSpliterators$IntWrappingSpliterator$$Lambda$170/25231275
> [4] java/util/stream/StreamSpliterators$IntWrappingSpliterator$$Lambda$170