Integrated: 8278351: Add function to retrieve worker_id from any context

[Per Liden]

On Tue, 7 Dec 2021 16:07:28 GMT, Per Liden <pliden at openjdk.org> wrote:

> The `worker_id` argument passed to `WorkerTask::work(uint worker_id)` is sometimes needed in contexts where it today can't be easily accessed, mainly because it's not feasible to pass this argument through many layers of semi-unrelated code. To solve this, I propose that we make the current `worker_id` accessible though a static function `WorkerThread::worker_id()`.
> 
> By doing this, we also pave the way for ZGC to remove its `ZTask` and `ZThread`, which are helper class to make the `worker_id` easily accessible in any context.
> 
> At the same time I propose that we remove `WorkerThread::_id`. This id identifies the actual worker thread. There is currently only one user of `WorkerThread::_id`, the `ReferenceProcessor`. However, we should use `WorkerThread::worker_id()` here instead. The only reason it doesn't use `worker_id` today is that it's not easily accessible in that context (the discover path).
> 
> Testing: Passed Tier1-3

This pull request has now been integrated.

Changeset: 7adf7f33
Author:    Per Liden <pliden at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/7adf7f3353ab81c5af3f2fc4c0fc9e4cf8905e32
Stats:     35 lines in 5 files changed: 9 ins; 10 del; 16 mod

8278351: Add function to retrieve worker_id from any context

Reviewed-by: eosterlund, kbarrett, ayang

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PR: https://git.openjdk.java.net/jdk/pull/6747