Re: [PATCH v3 1/3] pidfd: allow pidfd_open() on non-thread-group leaders

I am already sleeping. I'll try to reply to other parts of your email
tomorrow but I am not sure, I will be very busy with family duties.

On 01/23, Tycho Andersen wrote:

quoted

quoted

 	__exit_signal(p);

and,  do_notify_pidfd() is called before __exit_signal() which does
__unhash_process() -> detach_pid(PIDTYPE_PID).

Doesn't this mean that pidfd_poll() can hang? thread_group_exited()
won't return true after do_notify_pidfd() above, not to mention that
thread_group_empty() is not possible if !thread_group_leader().

I was wondering about this too, but the test_non_tgl_poll_exit test in
the next patch tests exactly this and works as expected.

Well, if release_task() completes __exit_signal() before the woken task
does thread_group_exited(), pid_task(PIDTYPE_PID) will return 0 and
pidfd_poll() won't hang.

But to be honest I can't understand test_non_tgl_poll_exit() at all. I don't
even understand why the process/thread created by fork_task_with_thread()
should ever exit. And why it creates the "writer" child... Never mind, too
late for me to read the code.

Oleg.