RFR: 8210926: vmTestbase/nsk/jvmti/scenarios/allocation/AP11/ap11t001/TestDescription.java failed with JVMTI_ERROR_INVALID_CLASS in CDS mode

Jiangli Zhou jiangli.zhou at oracle.com
Fri Sep 28 14:08:06 UTC 2018

Please review the fix for JDK-8210926. This is a bug in the CDS code 
that's exposed by JvmtiEnv::GetLoadedClasses(), and can be manifested in 
different failures with the following tests:



webrev: http://cr.openjdk.java.net/~jiangli/8210926/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8210926

SystemDictionary::add_to_hierarchy() sets a InstanceKlass init_state to 
‘loaded’ right before it is added to the the SystemDictionary. 
JvmtiEnv::GetLoadedClasses() retrieves loaded classes’ (InstanceKlasses 
in 'loaded' state and arrays) mirrors (Class objects). At CDS dump time, 
a InstanceKlass::_init_state is reset back to 'loaded' state before 
writing out the archived data. At runtime during loading of a shared 
class, there is a 'brief' moment JvmtiEnv::GetLoadedClasses() in another 
thread could see a shared class in ‘loaded’ state without mirror. NULL 
mirror is not the only issue, other fields of the shared InstanceKlass 
may not be setup properly before SystemDictionary::add_to_hierarchy(). 
To fix the issue, we need to reset to _init_state to 'allocated' state 
before writing out the archived classes at dump time.

Verified the fix with running ClassesByName2Test.java using mach5 
(thanks Chris for providing the reproducible case). Tested with tier1 - 
tier3 in both default CDS mode and no CDS mode.


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