[jdk17u-dev] RFR: 8349988: Change cgroup version detection logic to not depend on /proc/cgroups

[Jonathan Dowland]

On Mon, 16 Feb 2026 20:27:31 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

> Please review this backport of the cgroup version detection logic which affects JDK 17 as well. Newer systems which are affected, like Ubuntu 2025-XX, get more commonly used. Therefore, I propose to backport it there too. The JDK 21 backport got shipped with the 21.0.10 update in January. The patch is not clean due to `nullptr` vs `NULL` differences and more context changes (e.g. [JDK-8261242](https://bugs.openjdk.org/browse/JDK-8261242) not in JDK 17). Since the patch is not clean anyway, I've included the one-liner of [JDK-8354878](https://bugs.openjdk.org/browse/JDK-8354878) right away.
> 
> Testing:
> - [x] GHA
> - [x] Container tests on cg v1 and cg v2 on Linux x86_64 (RHEL 8 and Fedora 42). Manual testing on an affected cg v2 system that container limits are detected.

I'm not sure how useful this is, but `CgroupSubsystemFactory.java` on master passes for me (prior to this change) so it doesn't seem a useful way to demonstrate the bug being fixed.
The modified version of the test in this PR fails against a build from master but not for a useful reason (`java.lang.UnsatisfiedLinkError: 'int jdk.test.whitebox.WhiteBox.validateCgroup(boolean, java.lang.String, java.lang.String, java.lang.String)'`). I recall a different test failing for me due to missing mem controller in `/proc/cgroups`, I'm going to see if I can figure out which one it was.

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PR Comment: https://git.openjdk.org/jdk17u-dev/pull/4271#issuecomment-3950875680