[jdk17u-dev] RFR: 8305425: Thread.isAlive0 doesn't need to call into the VM

[Martin Doerr]

On Tue, 13 Jun 2023 09:02:28 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Unclean backport to improve `Thread.isAlive` performance, and provide grounds for more backports in the area.
> 
> The majority of conflicts are due to integration of Loom in JDK 19, which reshaped some Thread code. I tried to change as little in 17u as possible to avoid the change fan-out.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug `tier1 tier2 tier3`
>  - [x] Linux AArch64 fastdebug `tier1 tier2 tier3`

LGTM. Thanks for backporting! Please consider removing an empty line.

src/hotspot/share/prims/jvm.cpp line 2979:

> 2977: 
> 2978: 
> 2979: 

Seems like we should better remove one empty line more (like original change).

src/java.base/share/classes/java/lang/Thread.java line 166:

> 164:      * non-zero when the thread is started, and reset to zero when the thread terminates.
> 165:      * A non-zero value indicates this thread isAlive().
> 166:      */

Shortened comment. Ok.

-------------

Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk17u-dev/pull/1425#pullrequestreview-1495186509
PR Review Comment: https://git.openjdk.org/jdk17u-dev/pull/1425#discussion_r1239843335
PR Review Comment: https://git.openjdk.org/jdk17u-dev/pull/1425#discussion_r1239846737