While trying to push the changes for 7190666 (which changed G1 and the PLABStats code), I got the following crash when the JPRT job was running Target linux_x64-fastdebug-c2-jvm98.

The crash was a SIGSEGV during the GC:

#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007fbba0929aa4, pid=30910, tid=1083550032
#
# JRE version: Java(TM) SE Runtime Environment (8.0-b56)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (25.0-b02-internal-201209181609.jcuthber.7190666-test-fastdebug mixed mode linux-amd64 compressed oops)
# Problematic frame:
# V [libjvm.so+0x4fdaa4] oopDesc::size()+0x34
#
# Core dump written. Default location: /opt/jprt/products/P1/specjvm98/core or core.30910
#
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp

The stack trace from the hs_err file is:

Stack: [0x000000004085a000,0x000000004095b000], sp=0x0000000040959e30, free space=1023k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x4fdaa4] oopDesc::size()+0x34
V [libjvm.so+0x4f9ddb] CardTableExtension::scavenge_contents_parallel(ObjectStartArray*, MutableSpace*, HeapWord*, PSPromotionManager*, unsigned int, unsigned int)+0x3cb
V [libjvm.so+0xb8cb94] OldToYoungRootsTask::do_it(GCTaskManager*, unsigned int)+0xc4
V [libjvm.so+0x754d19] GCTaskThread::run()+0x199
V [libjvm.so+0xaf6e28] java_start(Thread*)+0x108