JVM hanging when using G1GC on JDK8 b78 or b79 (Linux 32 bit)

Uwe Schindler uschindler at apache.org
Tue Mar 5 13:48:40 PST 2013


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 difference.

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 with: https://builds.apache.org/job/Lucene-Artifacts-trunk/2212/artifact/lucene/dist/)
- 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 -XX:+UseConcMarkSweepGC"

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
uschindler at apache.org 
Apache Lucene PMC Member / Committer
Bremen, Germany

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