Hey Michael,
While working on pidfd Jann and I realized that TIDs don't get listed in
ls -al /proc
which is intended behavior. However, the directories for them still
exist i.e.
ls -al /proc/<tid>
works perfectly fine and so by extension do things like
cat /proc/<tid>/status.
This is information was new to us, as it was for some other people as
well. Afaict, the manpage for procfs doesn't mention this behavior at
all. I think it really should as this quite some implications:
- threads can be accessed via open("/proc/<tid>", ...) just as
thread-group leaders can
- all files that are available for thread-group leaders are available
for threads as well (This is not the case when going through
/proc/<pid>/task/<tid>.)
(Implementation-wise this means that threads are available once as
through tgid_proc_operations and once through tid_proc_operations but
that detail probably doesn't need to show up in the manpage.)
This is apparently part of the API so we should really document it. :)
Thanks!
Christian
