[jdk21u-dev] Integrated: 8331572: Allow using OopMapCache outside of STW GC phases

[Aleksey Shipilev]

On Tue, 28 May 2024 09:44:28 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Unclean backport to improve GC and general stack walk performance when walking interpreted frames.
> 
> This is one of few backports that gets `OopMapCache` behavior similar to mainline. This makes [JDK-8335409](https://bugs.openjdk.org/browse/JDK-8335409) backport easier, because it avoids lots of conflicts, resolving which might introduce surprising bugs. Aligning this code with mainline makes accidents less likely.
> 
> The point of uncleanliness comes from the way we hook up the cleanup notifications to Service Thread. In later JDKs, [JDK-8329488](https://bugs.openjdk.org/browse/JDK-8329488) made Service Thread wake up regularly to do various cleanups. In JDK 21, we still need to hook up the clean up to the "usual" place in safepoint epilog.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `all`

This pull request has now been integrated.

Changeset: ed77abd4
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.org/jdk21u-dev/commit/ed77abd487b53c845b6242174a2928174f121143
Stats:     117 lines in 12 files changed: 75 ins; 14 del; 28 mod

8331572: Allow using OopMapCache outside of STW GC phases
8334594: Generational ZGC: Deadlock after OopMap rewrites in 8331572

Reviewed-by: phh
Backport-of: d999b81e7110751be402012e1ed41b3256f5895e

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PR: https://git.openjdk.org/jdk21u-dev/pull/610