RFR: 8302744: Refactor Hotspot container detection code

[Severin Gehwolf]

On Fri, 3 May 2024 22:01:38 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Please review this container detection code refactoring in hotspot. The main point of this is to
>> 
>> - get rid of the `GET_CONTAINER_INFO` macros which hide too many things under the hood
>> - prevent refactoring of the code (since `GET_CONTAINER_INFO` macros short-return and are therefore not portable; at least not without some risk)
>> - make the code easier to understand
>> - allow for better testing via `gtest`
>> - separate multi-line parsing from single line parsing for clarity.
>> 
>> Testing:
>> - [x] GHA
>> - [x] `gtest:cgroupTest` tests
>> - [x] Container tests on Linux with cgroup v1 (legacy) and cgroup v2. All pass.
>> 
>> Thoughts?
>
> src/hotspot/os/linux/cgroupSubsystem_linux.hpp line 193:
> 
>> 191: PRAGMA_DIAG_PUSH
>> 192: PRAGMA_FORMAT_NONLITERAL_IGNORED
>> 193: template <typename T> int cg_file_multi_line_ctrl(CgroupController* c,
> 
> This always bothered me: If the first argument is a pointer to a `CgroupController`, then why isn't this just a method for that object? No need to for the `c == nullptr` check then either.

Good question. I hadn't considered it. Let me explore that option a bit and I'll get back to you.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19060#discussion_r1590682904