RFR: Minor changes to `StructuredTaskScope`
Paul Sandoz
psandoz at openjdk.java.net
Mon Apr 11 21:00:33 UTC 2022
Some suggested minor changes to `StructuredTaskScope` source while reviewing the code.
Overall I like how this approach has boiled down to about as simple as it can get while supporting the constraints of structured concurrency (thanks in no small part to `ThreadFlock`).
I think it should be possible to simplify the subclass implementations if the values of `Future.State` were comparable as in `RUNNING` < `CANCELED` < `FAILED` < `SUCCESS`. Otherwise, introducing that internally could also simplify and avoid the task scopes holding on unnecessarily to futures that are not operated on after join. I was reluctant to make such a change here but could propose as a separate PR.
I was uncertain if the `ShutdownOnSuccess.result` methods and the various exception returning/operating methods on `ShutdownOnFailure` should be constrained to throw if called before `join` has completed. Otherwise, we should specify that if operated on before `join` has completed then the results are unspecified.
(There might be a simple way for join to return something other than `this`, thereby avoiding this issue, with some additional complexity, but I suspect you have already thought of that and took the minimal route.)
I presume there is an implicit happens-before edge on `join` that we can make explicit and specify?
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Commit messages:
- Minor changes.
Changes: https://git.openjdk.java.net/loom/pull/142/files
Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=142&range=00
Stats: 39 lines in 1 file changed: 8 ins; 4 del; 27 mod
Patch: https://git.openjdk.java.net/loom/pull/142.diff
Fetch: git fetch https://git.openjdk.java.net/loom pull/142/head:pull/142
PR: https://git.openjdk.java.net/loom/pull/142
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