8351997: AArch64: Interpreter volatile reference stores with G1 are not sequentially consistent

[shipilev]

Fixes AArch64 memory ordering problem. Readily manifests in new jcstress tests; there are sightings of related problems in JSR 133 tests. The patch is not clean, because JDK-8301996 is in the way, and it is IMO too risky to backport. I resolved some hunks to match the intended behavior, after checking do_oop_store clobbers the same r3 as in mainline.

Additional testing:

• Linux AArch64 server release, jcstress RefDekker test now passes
• Linux AArch64 server release, jcstress seqcst.volatiles.ref tests now pass
• Linux AArch64 server release, jcstress all tests now pass
• Linux AArch64 server fastdebug, all

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8351997 needs maintainer approval

Issue

• JDK-8351997: AArch64: Interpreter volatile reference stores with G1 are not sequentially consistent (Bug - P2 - Approved)

Reviewers

• Paul Hohensee (@phohensee - Reviewer)
• Andrew Haley (@theRealAph - Reviewer)
• Erik Österlund (@fisk - Committer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk21u-dev.git pull/1905/head:pull/1905
$ git checkout pull/1905

Update a local copy of the PR:
$ git checkout pull/1905
$ git pull https://git.openjdk.org/jdk21u-dev.git pull/1905/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1905

View PR using the GUI difftool:
$ git pr show -t 1905

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk21u-dev/pull/1905.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back shade! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@shipilev 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:

8351997: AArch64: Interpreter volatile reference stores with G1 are not sequentially consistent

Reviewed-by: phh, aph, eosterlund

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 37 new commits pushed to the master branch:

• ef6acda: 8310974: NMT: Arena diffs miss the scale
• c9fb719: 8308633: Increase precision of timestamps in g1 log
• 9ccd857: 8309899: Rename PtrQueueSet::buffer_size()
• ... and 34 more: https://git.openjdk.org/jdk21u-dev/compare/9a6ef52b82e66dfd5779f66113c28371ff2fd776...master

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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 00: Full (91da5f7a)

[openjdk]

⚠️ @shipilev This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[shipilev]

@theRealAph, @fisk -- take a look as well?

[fisk]

Looks good.

[shipilev]

/approval request Fixes the corner case in AArch64 interpreter, manifests as memory model problem. jcstress RefDekker and seqcst.volatiles.ref fail without the fix, pass with it. All other tests also pass. The change was in mainline for 3 weeks without bugtail. Even though the fix is relatively fresh, it is well-understood. 21u version differs a bit from mainline version, see 21u PR.

[openjdk]

@shipilev
8351997: The approval request has been created successfully.

[shipilev]

Push approval granted. Here we go.

/integrate

[openjdk]

Going to push as commit 729f100.
Since your change was applied there have been 37 commits pushed to the master branch:

• ef6acda: 8310974: NMT: Arena diffs miss the scale
• c9fb719: 8308633: Increase precision of timestamps in g1 log
• 9ccd857: 8309899: Rename PtrQueueSet::buffer_size()
• ... and 34 more: https://git.openjdk.org/jdk21u-dev/compare/9a6ef52b82e66dfd5779f66113c28371ff2fd776...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 729f100.

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