Is it really needed on linux to recurse into /proc/[PID]/task/?

[GuillaumeGomez]

From what I can see, all PIDs listed in the task subfolder are directly present in /proc, which means that the same information is retrieved twice unless I missed something. Is it really necessary to recurse into task then?

[BenBE]

Yes.

That recursion into /proc/[PID]/task/ is done, as some (thread-specific) information are only available from there (pure pthreads don't show up in /proc, but only in the task directory). Also the main /proc does list processes and not POSIX threads.

To demonstrate, here's a quick screenshot:

The process belongs to a python script that both uses pthreads (visible on the right) as well as forked a sub-process (PID 211606 in that screenshot).

[GuillaumeGomez]

Thanks for the explanations!

[GuillaumeGomez]

Interesting information I discovered in the man page:

The /proc/[tid] subdirectories are not visible when iterating through /proc with get‐
dents(2) (and thus are not visible when one uses ls(1) to view the contents of /proc).

So that definitely answers the question. Thanks again!