Lots of JDI tests crash in the debugee process when run with -XX:+UseConcMarkSweepGC. The crash is:

#
# An unexpected error has been detected by Java Runtime Environment:
#
# Internal Error (/BUILD_AREA/jdk7/hotspot/src/share/vm/runtime/mutexLocker.cpp:125), pid=21193, tid=2
# Error: must own lock UNKNOWN

Stack looks like:
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x130fa44];; void VMError::report(outputStream*)+0x784
V [libjvm.so+0x1310a13];; void VMError::report_and_die()+0x4c3
V [libjvm.so+0x73cc3b];; void report_fatal_vararg(const char*,int,const char*,...)+0x10b
V [libjvm.so+0xf23bad];; void assert_locked_or_safepoint(const Monitor*)+0xad
V [libjvm.so+0x671aba];; HeapWord*CompactibleFreeListSpace::block_start(const
void*)const+0x2a
V [libjvm.so+0x839e48];; void GenerationBlockStartClosure::do_space(Space*)+0x38
V [libjvm.so+0x6c6b0a];; void ConcurrentMarkSweepGeneration::space_iterate(SpaceClosure*,bool)+0x1a
V [libjvm.so+0x837a18];; HeapWord*Generation::block_start(const void*)const+0x38
V [libjvm.so+0x81e031];; HeapWord*GenCollectedHeap::block_start(const void*)const+0x131
V [libjvm.so+0xef8c72];; methodOop methodOopDesc::method_from_bcp(unsigned char*)+0x52
V [libjvm.so+0x512bff];; Bytecodes::Code Bytecodes::non_breakpoint_code_at(unsigned char*,methodOop)+0x2f
V [libjvm.so+0x901f8a];; void InterpreterRuntime::resolve_get_put(JavaThread*,Bytecodes::Code)+0x97a
j nsk.jdi.MethodEntryRequest.addInstanceFilter.instancefilter001a.methodForCommunication()V+0
j nsk.jdi.MethodEntryRequest.addInstanceFilter.instancefilter001a.main([Ljava/lang/String;)V+56
v ~StubRoutines::call_stub

hs.err.cms stack attached.

There are about 71 affected tests. Run this command for one such test (all one line)

runnsk -XX:+UseConcMarkSweepGC nsk/jdi/MethodEntryRequest/addInstanceFilter/instancefilter001 -jdk $JAVA_HOME -tongajdk $JAVA_HOME

This crash occurs with the b24 fastdebug jdk. I searched for duplicates but didn't find any.