RFR: Keep root bits until the end of partial

[Aleksey Shipilev]

Actually that was wrong. We still need to clean root bits at the first step,
because partial may get cancelled on OOME, leaving roots set indefinitely:
  http://cr.openjdk.java.net/~shade/shenandoah/partial-keeproots/webrev.02/

-Aleksey

On 06/14/2017 03:34 PM, Zhengyu Gu wrote:
> Okay.
> 
> -Zhengyu
> 
> On 06/14/2017 09:31 AM, Aleksey Shipilev wrote:
>> We need to keep region->is_root bit until partial is over, because otherwise
>> hs_err from the mid-partial crash looks misleading: it could say that some
>> region is not root, while it actually is!
>>
>> See:
>>   http://cr.openjdk.java.net/~shade/shenandoah/partial-keeproots/webrev.01/
>>
>> Thanks,
>> -Aleksey
>>