8270869: G1ServiceThread may not terminate

[kimbarrett]

Please review this fix of a rare race in G1ServiceThread termination that
can lead to the thread not terminating in a timely manner.

Testing:
mach5 tier1

---

Progress

• Change must not contain extraneous whitespace
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Issue

• JDK-8270869: G1ServiceThread may not terminate

Reviewers

• Albert Mingkun Yang (@albertnetymk - Committer) ⚠️ Review applies to e065a51
• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to e065a51

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/4819/head:pull/4819
$ git checkout pull/4819

Update a local copy of the PR:
$ git checkout pull/4819
$ git pull https://git.openjdk.java.net/jdk pull/4819/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 4819

View PR using the GUI difftool:
$ git pr show -t 4819

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/4819.diff

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[openjdk]

@kimbarrett The following label will be automatically applied to this pull request:

• hotspot-gc

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[mlbridge]

Webrevs

• 01: Full - Incremental (0848dcd4)
• 00: Full (e065a515)

[albertnetymk]

Only a minor comment on the style; I think not using else-if is clearer: the early-return handles the exiting condition, and the other two cases depend on the task queue state.

[tschatzl]

Looks good, same comment about the use of the else if, but I'm good either way.

[openjdk]

@kimbarrett This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8270869: G1ServiceThread may not terminate

Reviewed-by: ayang, tschatzl

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[kimbarrett]

Looks good, same comment about the use of the else if, but I'm good either way.

I think that looks weird; the if-ladder covers all cases, and splitting it up makes that seem less obvious to me. Also, if I were to split it up I would probably write the exiting case as
if (should_terminate()) return;
which I know Thomas has a preference against.

Aside: I think this function might get rewritten as part of what I'm thinking about doing under JDK-8270870, which will probably render this discussion moot.

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 7f35e5b.

[openjdk]

@kimbarrett Pushed as commit 7f35e5b.

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