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List:       openjdk-hotspot-dev
Subject:    Re: [9] RFR(S): 8054402: "klass->is_loader_alive(_is_alive)) failed: must be alive" for anonymous cl
From:       Vladimir Kozlov <vladimir.kozlov () oracle ! com>
Date:       2014-08-12 13:49:19
Message-ID: 53EA1B5F.2080502 () oracle ! com
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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


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