RFR (XS) 8223570: Shenandoah needs to acquire lock before CLDG::clear_claimed_marks

[Aleksey Shipilev]

On 5/8/19 2:11 PM, Roman Kennke wrote:
> (how has that not failed before? Also, we shall revisit this clear_claimed_marks in traversal. It
> should not be necessary and only extend the traversal.)

Yes. New assert, recently committed. It probably fails silently otherwise. Pushed.

> Roman
> 
>> Bug:
>>    https://bugs.openjdk.java.net/browse/JDK-8223570
>>
>> New assert fails and exposes this legit GC bug. Shenandoah does CLDG::clear_claimed_marks in two
>> places, one under the safepoint (which is fine for that assert), and another one in concurrent
>> thread, which fails.

-Aleksey