RFR: 8169423: Infinite loop in G1's ConcurrentMarkThread

[Kim Barrett]

> On Nov 15, 2016, at 5:11 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Hi,
> 
> On Fri, 2016-11-11 at 15:38 -0500, Kim Barrett wrote:
>> Please review this fix of a potential (though quite rare) infinite
>> loop in G1's concurrent mark thread's service routine.
>> 
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8169423
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8169423/webrev.00/
>> 
>> Testing:
>> JPRT
> 
>   looks good.

Thanks.

> It would be nice to have some information about during which phase the
> concurrent mark stack overflowed. This seems out of scope though, I
> created JDK-8169706.

Agreed.  Thanks for filing that.

I had originally guessed mark_from_roots might loop on overflow, but I don’t
see any sign of that.  The duplicative debug logging message that I removed
was certainly suggestive of that, explicitly saying the restart is because of
overflow “in Remark”. 

> Thomas