RFR(T) 8222086: CodeCache::UnloadingScope needs to preserve and restore previous IsUnloadingBehavior

[Zhengyu Gu]

Thank you, Erik.

-Zhengyu

On 4/8/19 8:58 AM, Erik Österlund wrote:
> Hi Zhengyu,
> 
> Looks good.
> 
> /Erik
> 
> On 2019-04-08 02:57, Zhengyu Gu wrote:
>> Shenandoah can (will) do concurrent class unloading, but also unloads 
>> classes at pauses, e.g. during full gc.
>>
>> Currently, CodeCache::UnloadingScope's destructor resets 
>> IsUnloadingBehaviour that is setup for concurrent class unloading, 
>> which results fatal crash during next concurrent unloading cycle.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8222086
>> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8222086/webrev.00/
>>
>>
>> Test:
>>   hotspot_gc on Linux x64 (fastdebug and release)
>>   Submit tests.
>>
>> Thanks,
>>
>> -Zhengyu
>