RFR 8199868: Support JNI critical functions in object pinning API

[Zhengyu Gu]

Offline discussion with Aleksey, he suggested that 
pin/unpin_critical_native_array methods can be made more generic as 
pin/unpin_object.

Updated webrev: http://cr.openjdk.java.net/~zgu/8199868/webrev.01/

Test:
   Reran all tests, submit-hs tests still clean.

Thanks,

-Zhengyu

On 04/06/2018 08:55 AM, Aleksey Shipilev wrote:
> On 04/04/2018 07:47 PM, Zhengyu Gu wrote:
>> Please review this patch that adds JNI critical native support to object pinning.
>>
>> Shenandoah does not block GC while JNI critical session is in progress. This patch allows it to pin
>> all incoming array objects before critical native call, and unpin them after call completes.
>>
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8199868
>> Webrev: http://cr.openjdk.java.net/~zgu/8199868/webrev.00/
> 
> Looks good to me, but somebody more savvy with runtime stub generation should take a closer look.
> 
> *) Should probably be "Why we are here?"
> 
> 2867   assert(Universe::heap()->supports_object_pinning(), "Why we here?");
> 
> 2876   assert(Universe::heap()->supports_object_pinning(), "Why we here?");
> 
> 
> Thanks,
> -Aleksey
>