[13] RFR (XS): 8225141: Better handling of classes in error state in fast class initialization checks

[Vladimir Ivanov]

Thanks, Dean.

Best regards,
Vladimir Ivanov

On 01/06/2019 02:14, dean.long at oracle.com wrote:
> Looks good.
> 
> dl
> 
> On 5/31/19 1:53 PM, Vladimir Ivanov wrote:
>> http://cr.openjdk.java.net/~vlivanov/8225141/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-8225141
>>
>> Fast class initialization checks don't properly handle classes in 
>> error state when performed from (previously) initializing thread.
>>
>> One way to fix it is to add one more fast path check 
>> (InstanceKlass::_init_state == being_initialized) into the barrier, 
>> but that would require significant changes, since both newly 
>> introduced checks (JDK-8223213 [1]) and existing C1 checks should be 
>> changed.
>>
>> What I propose is to set InstanceKlass::_init_thread only for the 
>> duration when the klass is in being_initialized state and reset it 
>> back to NULL when changing class state. It makes existing 
>> "_init_thread == current_thread" check equivalent to "_init_state == 
>> being_initialized && _init_thread == current_thread".
>>
>> Testing: hs-precheckin-comp, tier1-4
>>
>> Best regards,
>> Vladimir Ivanov
>>
>> [1] https://bugs.openjdk.java.net/browse/JDK-8223213
>