NOTE_TRACK, EVFILT_PROC, kqueue, and subreapers

[Konstantin Belousov]

On Sun, Dec 11, 2016 at 01:46:38PM +0100, Jilles Tjoelker wrote:
> As reported in https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=213928
> reapers do not receive SIGCHLD when inheriting zombies, although they do
> receive SIGCHLD when an inherited descendant process later terminates
> and are awakened when in a wait call for a matching process. This should
> probably be fixed.
I agree, in principle.  Could you update your tests/sys/kern/reaper.c to
include this scenario ?

Untested change to the kernel side is below.

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index f4f453c3556..92899740eef 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -455,6 +455,12 @@ exit1(struct thread *td, int rval, int signo)
 
 		if (!(q->p_flag & P_TRACED)) {
 			proc_reparent(q, q->p_reaper);
+			if (q->p_state == PRS_ZOMBIE) {
+				PROC_LOCK(q->p_reaper);
+				pksignal(q->p_reaper, SIGCHLD, q->p_ksi);
+				wakeup(q->p_reaper);
+				PROC_UNLOCK(q->p_reaper);
+			}
 		} else {
 			/*
 			 * Traced processes are killed since their existence