RFR: 8372584: [Linux]: Replace reading proc to get thread user CPU time with clock_gettime [v3]

[Thomas Stuefe]

On Tue, 2 Dec 2025 09:15:31 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Using a positive outcome like success to encode the outcome make it possible to return like so `return success ? os::Linux::thread_cpu_time(clockid) : -1;`. I prefer having the `-1` at the end as I find this reads easier. If we encode a failure we would need to write `return !failure ? os::Linux::thread_cpu_time(clockid) : -1;`. Hence, I would prefer keeping this as is as double-negatives may be harder to parse.
>
> Okay but you are setting up a usage requirement without documenting anywhere that that requirement exists.

I would prefer if we kept using the standard. When in Rome...

What we often do is this:


bool get_thread_clockid(Thread* thread, bool total, clock_id_t* is);


or, alternatively, what David wrote.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28556#discussion_r2581600332