Integrated: 8263375: Support stack watermarks in Zero VM

[Aleksey Shipilev]

On Thu, 8 Jul 2021 16:48:26 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Zero VM supports most of GCs. Since JDK 16, Shenandoah uses stack watermarks, so Zero has to support those if Shenandoah+Zero support is to remain. This PR adds the stack watermark support in Zero VM. This should also be useful as other projects, notably Loom, mature and depend on stack watermarks.
> 
> Zero already calls into Hotspot safepoint machinery to do things, and it seems only the hooks for `on_iteration` and `on_unwind` are missing. AFAICS, Zero only has on-return safepoints, renamed it to be more precise.
> 
> @fisk, do you see any obvious problems with this patch?
> 
> Additional testing:
>  - [x] Linux x86_64 Zero `hotspot_gc_shenandoah` now passes

This pull request has now been integrated.

Changeset: 857a930b
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/857a930bde8b53f77a23737f4ca6ff8f3da2af66
Stats:     58 lines in 5 files changed: 37 ins; 14 del; 7 mod

8263375: Support stack watermarks in Zero VM

Reviewed-by: eosterlund

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PR: https://git.openjdk.java.net/jdk/pull/4728