NOTE_TRACK, EVFILT_PROC, kqueue, and subreapers
Konstantin Belousov
kostikbel at gmail.com
Mon Dec 12 11:12:25 UTC 2016
On Sun, Dec 11, 2016 at 11:23:28PM +0100, Jilles Tjoelker wrote:
> On Sun, Dec 11, 2016 at 07:54:51PM +0200, Konstantin Belousov wrote:
> > 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 ?
>
> I tested with the patch below. The new test case
> reaper_sigchld_child_first already passes and I have marked
> reaper_sigchld_grandchild_first as an expected timeout.
>
> > 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
>
> This change makes reaper_sigchld_grandchild_first pass.
>
> The wakeup added here is redundant with the one a few lines above:
> if (q != NULL) /* only need this if any child is S_ZOMB */
> wakeup(q->p_reaper);
I removed additional wakeup, it should be innocent. Might be the better
change is to remove the lines you cited above and do wakeups inside the
loop after reparenting. But I kept it that way for now.
>
> This is also clear because reaper_wait_grandchild_first already passes.
>
> Index: tests/sys/kern/reaper.c
Thank you, I verified that all tests pass with the patched kernel and
removed timeouts from your reaper_sigchld_*child_first new tests.
The kernel chunk is committed as r309886, please commit tests.
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