[PATCH 0/1] cgroup: avoid the unnecessary list_add(dying_tasks) in cgroup_exit()

[Oleg Nesterov]

Hello,

Sorry for delay and for confusing you in our previous discussion
here https://lore.kernel.org/all/20240610105028.GA21586@xxxxxxxxxx/

No, cgroup_exit() can't rely on group_dead, this is racy.

And no, we can't shift css_set_skip_task_iters/etc from cgroup_release()
to cgroup_exit(), an execing sub-thread can change the group leader.

Let me at least send the simple patch which looks "obviously good" to me.

I would really like to remove the usage of signal->live in cgroup.c, but
so far I do not see a simple solution.

With or without this change cgroup.procs can be empty but cgroup.threads
is not. But at least the exiting sub-threads which have already passed
atomic_dec_and_test() should call cgroup_exit() "soon".

Oleg.