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

[Erik Österlund]

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