Integrated: 8255837: Shenandoah: Remove ShenandoahConcurrentRoots class

[Zhengyu Gu]

On Wed, 27 Jan 2021 14:14:50 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

> The class was introduced for 2 purposes:
> 1) a platform supports concurrent class unloading (e.g. the platform supports nmethod_entry_barrier) 
> 2) should perform concurrent class unloading for particular gc cycle (e.g. STW vs. concurrent GC)
> 
> Now, concurrent class unloading is supported on all Shenandoah supported platforms. Furthermore, STW and concurrent GC are isolated (JDK-8255765), the class not only becomes superfluous, but also looks weird, e.g.
> 
> `bool do_nmethods = heap->unload_classes() && !ShenandoahConcurrentRoots::can_do_concurrent_class_unloading(); `
> 
> Test:
> - [x] hotspot_gc_shenandoah Linux x86_64 and x86_32
> - [x] nightly

This pull request has now been integrated.

Changeset: 22bfa5b0
Author:    Zhengyu Gu <zgu at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/22bfa5b0
Stats:     165 lines in 16 files changed: 0 ins; 124 del; 41 mod

8255837: Shenandoah: Remove ShenandoahConcurrentRoots class

Reviewed-by: rkennke

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PR: https://git.openjdk.java.net/jdk/pull/2262