8261660: AArch64: Race condition in stub code generation for LSE Atomics

[theRealAph]

Temporary fix for race condition.

There's a narrow race condition in the code which generates LSE Atomic stubs and enables them for use by the runtime. DIsable LSE stub generation for now.

/cc hotspot

---

Progress

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

Issue

• JDK-8261660: AArch64: Race condition in stub code generation for LSE Atomics

Reviewers

• Daniel D. Daugherty (@dcubed-ojdk - Reviewer)
• Andrew Dinn (@adinn - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/2553/head:pull/2553
$ git checkout pull/2553

[bridgekeeper]

👋 Welcome back aph! 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]

@theRealAph
The hotspot label was successfully added.

[mlbridge]

Webrevs

• 00: Full (220e936)

[dcubed-ojdk]

Looks okay, but I have to wonder if the rest of the template changes
in src/hotspot/os_cpu/linux_aarch64/atomic_linux_aarch64.hpp
that were made by https://bugs.openjdk.java.net/browse/JDK-8261027
also need to be backed out? Please clarify.

[adinn]

Yes, this will be fine for now until the code generation and update of the code pointers can be corrected to happen in the right order.

[openjdk]

@theRealAph 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:

8261660: AArch64: Race condition in stub code generation for LSE Atomics

Reviewed-by: dcubed, adinn

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 3 new commits pushed to the master branch:

• 6675775: 8253702: BigSur version number reported as 10.16, should be 11.nn
• 33fcd32: 8261659: JDK-8261027 causes a Tier1 validate-source failure
• 3aa1b4c: 8261623: reference to javac internals in Extern class

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.

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

[dcubed-ojdk]

Thanks for the explanation. Thumbs up.

This is a trivial fix and does not have to wait for 24 hours.

[adinn]

@dcubed-ojdk A complete fix merely requires writing the generated stub code before updating the stub function pointers. With this change all that happens is that those pointers continue pointing to the default routines. There is no point backing out the rest of the code given that it will almost all be needed.

[theRealAph]

/integrate

[openjdk]

@theRealAph Since your change was applied there have been 4 commits pushed to the master branch:

• 28163a9: 8261652: Remove some dead comments from os_bsd_x86
• 6675775: 8253702: BigSur version number reported as 10.16, should be 11.nn
• 33fcd32: 8261659: JDK-8261027 causes a Tier1 validate-source failure
• 3aa1b4c: 8261623: reference to javac internals in Extern class

Your commit was automatically rebased without conflicts.

Pushed as commit a305743.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.