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From Tommaso Teofili <tommaso.teof...@gmail.com>
Subject Fwd: JVM hanging when using G1GC on JDK8 b78 or b79 (Linux 32 bit)
Date Wed, 06 Mar 2013 16:05:48 GMT
there's a strange (interesting?) bug in latest Java8 update which is
triggered by the UIMA Lucene Analyzers tests [1]

[1] : http://markmail.org/thread/wtz2mnpx7b63lxjn

---------- Forwarded message ----------
From: Uwe Schindler <uschindler@apache.org>
Date: 2013/3/5
Subject: JVM hanging when using G1GC on JDK8 b78 or b79 (Linux 32 bit)
To: hotspot-gc-dev@openjdk.java.net, hotspot-dev@openjdk.java.net
Cc: Dawid Weiss <dweiss@apache.org>, dev@lucene.apache.org


since a few month we are extensively testing various preview builds of JDK
8 for compatibility with Apache Lucene and Solr, so we can find any bugs
early and prevent the problems we had with the release of Java 7 two years
ago. Currently we have a Linux (Ubuntu 64bit) Jenkins machine that has
various JDKs (JDK 6, JDK 7, JDK 8 snapshot, IBM J9, older JRockit)
installed, choosing a different one with different hotspot and garbage
collector settings on every run of the test suite (which takes approx.
30-45 minutes).

JDK 8 b79 works so far very well on Linux, we found some strange behavior
in early versions (maybe compiler errors), but no longer at the moment.
There is one configuration that constantly and reproducibly hangs in one
module that is tested: The configuration uses JDK 8 b79 (same for b78), 32
bit, and G1GC (server or client does not matter). The JVM running the tests
hangs irresponsible (jstack or kill -3 have no effect/cannot connect,
standard kill does not stop it, only kill -9 actually kills it). It can be
reproduced in this Lucene module 100% (it hangs always).

I was able to connect with GDB to the JVM and get a stack trace on all
threads (see attachment, dump.txt). As you see all threads of G1GC seem to
hang in a syscall (os:park(), a conditional wait in pthread library).
Unfortunately that’s all I can give you. A Java stacktrace is not possible
because the JVM reacts on neither kill -3 nor jstack. With all other
garbage collectors it passes the test without hangs in a few seconds, with
32 bit G1GC it can stand still for hours. The 64 bit JVM passes with G1GC,
so only the 32 bit variant is affected. Client or Server VM makes no

To reproduce:
- Use a 32 bit JDK 8 b78 or b79 (tested on Linux 64 bit, but this should
not matter)
- Download Lucene Source code (e.g. the snapshot version we were testing
- change to directory lucene/analysis/uima and run:
        ant -Dargs="-server -XX:+UseG1GC" -Dtests.multiplier=3
-Dtests.jvms=1 test
After a while the test framework prints "stalled" messages (because the
child VM actually running the test no longer responds). The PID is also
printed. Try to get a stack trace or kill it, no response. Only kill -9
helps. Choosing another garbage collector in the above command line makes
the test finish after a few seconds, e.g. -Dargs="-server

I posted this bug report directly to the mailing list, because with earlier
bug reports, there seem to be a problem with bugs.sun.com - there is no
response from any reviewer after several weeks and we were able to help to
find and fix javadoc and javac-compiler bugs early. So I hope you can help
for this bug, too.


Uwe Schindler
Apache Lucene PMC Member / Committer
Bremen, Germany

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