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

[David Holmes]

Hi Jiangli,

This seems a little odd:

2303   // Unlink the class
2304   if (is_linked()) {
2305     unlink_class();
2306   }
2307
2308   _init_state = allocated;

unlink_class() will set the _init_state to loaded then we set it back to 
allocated.

There's a typo in a comment "the the".

Thanks,
David
(Literally running out the door :) )

On 28/09/2018 10:08 AM, Jiangli Zhou wrote:
> 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:
> 
>    com/sun/jdi/ClassesByName2Test.java
> vmTestbase/nsk/jvmti/scenarios/allocation/AP11/ap11t001/TestDescription.java 
> 
>    runtime/RedefineTests/ModifyAnonymous.java
> 
> 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.
> 
> Thanks,
> Jiangli
> 
>