RFR: 8186035: Klass::decode_klass_not_null() asserted on bad oop

[Stefan Karlsson]

Thanks, StefanJ.

StefanK

On 2017-08-11 14:03, Stefan Johansson wrote:
>
>
> On 2017-08-11 12:35, Thomas Schatzl wrote:
>> Hi Stefan,
>>
>> On Fri, 2017-08-11 at 11:33 +0200, Stefan Karlsson wrote:
>>> Hi all,
>>>
>>> Please review this patch to temporarily remove a failing assert in
>>> G1.
>>>
>>> http://cr.openjdk.java.net/~stefank/8186035/webrev.01/
>>> https://bugs.openjdk.java.net/browse/JDK-8186035
>>    looks good. Thanks for taking care of this.
> +1
> StefanJ
>
>>
>>> The problem is that during initial marking, multiple threads might
>>> race to copy an object and they will all try to mark the new copy if
>>> it ends up in the old gen. In the marking code, there's an assert
>>> that the object should be valid. However, only the thread that won
>>> the race to copying the object is allowed to read the contents of the
>>> 'to' copy, and all other threads might see garbage and could fail on
>>> this assert.
>>>
>>> The removal of the assert is an interim solution, to get rid of
>>> failure in our testing. I'm working on another fix for this, where
>>> only the winning thread is marking newly copied object. See:
>>> https://bugs.openjdk.java.net/browse/JDK-8186133
>>>
>>    also, thanks for that.
>>
>> Thomas
>>
>