RFR: 8284199: Implementation of Structured Concurrency (Incubator)

[Maurizio Cimadamore]

On Thu, 19 May 2022 13:05:54 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> This is the implementation of JEP 428: Structured Concurrency (Incubator).
> 
> This is a non-final API that provides a gentle on-ramp to structure a task as a family of concurrent subtasks, and to coordinate the subtasks as a unit.

Marked as reviewed by mcimadamore (Reviewer).

src/jdk.incubator.concurrent/share/classes/jdk/incubator/concurrent/StructuredTaskScope.java line 88:

> 86:  * {@code join} method after forking.
> 87:  *
> 88:  * <p> StructuredTaskScope defines the {@link #shutdown() shutdown} method to shut down a

This sentence, because of the place where it appears, is a bit confusing. So far we only know about the fact that a scope has an owner thread. So it seems odd that shutdown could be called _while_ the owner thread is waiting on a `join`. Of course, then you read what's next, and you discover that: (a) shutdown might be called by a custom scope subclass and that (b) shutdown is confined to the threads contained in this task scope - but this definition is only given much later.

src/jdk.incubator.concurrent/share/classes/jdk/incubator/concurrent/StructuredTaskScope.java line 353:

> 351:      *
> 352:      * <p> The {@code handleComplete} method should be thread safe. It may be
> 353:      * invoked by several threads at around the same.

Something is missing? E.g. "at around the same TIME" ? (I'd suggest just using "concurrently")

src/jdk.incubator.concurrent/share/classes/jdk/incubator/concurrent/StructuredTaskScope.java line 376:

> 374:      *
> 375:      * <p> If this task scope is {@linkplain #shutdown() shutdown} (or in the process
> 376:      * of shutting down) then {@code fork} returns a Future representing a {@link

Future in plaintext?

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PR: https://git.openjdk.java.net/jdk/pull/8787