RFR: 8322420: [Linux] cgroup v2: Limits in parent nested control groups are not detected [v12]

[Jan Kratochvil]

On Thu, 11 Jul 2024 10:39:23 GMT, Severin Gehwolf <sgehwolf at openjdk.org> wrote:

>> Jan Kratochvil has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 103 commits:
>> 
>>  - Fix the gtest
>>  - fix compilation warning
>>  - fix the gtest
>>  - less refactorizations
>>  - remove not a real backward compat.
>>  - whitespace
>>  - less refactorizations
>>  - reduce refactorizations
>>  - Fix caching
>>  - Merge branch 'master' into master-cgroup
>>  - ... and 93 more: https://git.openjdk.org/jdk/compare/537d20af...060e7688
>
> test/hotspot/gtest/runtime/test_cgroupSubsystem_linux.cpp line 1:
> 
>> 1: /*
> 
> Why are those test changes needed?

As before there was for V1:

    CgroupV1Controller* ctrl = new CgroupV1Controller( (char*)testCases[i]->root_path,
                                                       (char*)testCases[i]->mount_path,
                                                       true /* read-only mount */);
    ctrl->set_subsystem_path((char*)testCases[i]->cgroup_path);

vs. for V2:

    CgroupV2Controller* ctrl = new CgroupV2Controller( (char*)testCases[i]->mount_path,
                                                       (char*)testCases[i]->cgroup_path,
                                                       true /* read-only mount */);

Which was error prone as both parameters were `char *` with different meaning.
Now it is all unified with the same parameters order, for V1:

    CgroupV1Controller* ctrl = new CgroupV1Controller( (char*)testCases[i]->root_path,
                                                       (char*)testCases[i]->mount_path,
                                                       true /* read-only mount */);
    ctrl->set_subsystem_path((char*)testCases[i]->cgroup_path);

and similarly V2:

    CgroupV2Controller* ctrl = new CgroupV2Controller( (char*)testCases[i]->root_path,
                                                       (char*)testCases[i]->mount_path,
                                                       true /* read-only mount */);
    ctrl->set_subsystem_path((char*)testCases[i]->cgroup_path);

That `set_subsystem_path` should be probably a part of the ctor but that is for a later refactorization.

Besides that for example `larger_than_max` should be a path but it did not start with a slash ('/') which did not matter as `TestController` did override+skip `subsystem_path()` underneath but then the whole testfile did not test much.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17198#discussion_r1677267509