8271215: Fix data races in G1PeriodicGCTask

[kimbarrett]

Please review this small change to G1PeriodicGCTask, eliminating unlikely
but possible data races with a concurrently running GC pause. An STS-joiner
is used to ensure there isn't a GC pause while doing the checks to decide
whether to perform a periodic GC.

Testing:
mach5 tier1

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8271215: Fix data races in G1PeriodicGCTask

Reviewers

• Ivan Walulya (@walulyai - Committer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/4899/head:pull/4899
$ git checkout pull/4899

Update a local copy of the PR:
$ git checkout pull/4899
$ git pull https://git.openjdk.java.net/jdk pull/4899/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 4899

View PR using the GUI difftool:
$ git pr show -t 4899

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/4899.diff

[bridgekeeper]

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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

• 00: Full (32907edd)

[shipilev]

Looks fine.

[openjdk]

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8271215: Fix data races in G1PeriodicGCTask

Reviewed-by: iwalulya, shade

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 2 new commits pushed to the master branch:

• e4295cc: 8270519: Move several vector helper methods to shared header file
• e627cae: 8270317: Large Allocation in CipherSuite

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[kimbarrett]

Thanks @walulyai and @shipilev for reviews.

[kimbarrett]

/integrate

[openjdk]

Going to push as commit f2c359a.
Since your change was applied there have been 3 commits pushed to the master branch:

• 36aefa3: 8270447: [IR Framework] Add missing compilation level restriction when using FlipC1C2 stress option
• e4295cc: 8270519: Move several vector helper methods to shared header file
• e627cae: 8270317: Large Allocation in CipherSuite

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit f2c359a.

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