RFR 8224875: Shenandoah: ParallelCleaning code unloading should take lock to protect shared code roots array

[Aleksey Shipilev]

On 5/29/19 1:29 PM, Zhengyu Gu wrote:
>> *) Since you moved the assert in ShenandoahCodeRoots::remove_nmethod, is it worth it to move it in
>> ShenandoahCodeRoots::add_nmethod too?
>>
> Sure.

So... should we make (add|remove)_nmethod symmetrical? If remove_* can acquire the lock, then add_*
should do that too?

> Updated webrev: http://cr.openjdk.java.net/~zgu/JDK-8224875/webrev.01/

Otherwise good.

-Aleksey