On Mon, Oct 09, 2017 at 12:15:46PM +0200, Martin Pieuchot wrote:
> To prevent an infinite loop, threads looking for events inside
> kqueue_scan(), insert a `marker' in the list. Such markers are
> not accounted and they are removed from the list as soon as the
> thread is finished or goes to sleep.
>
> Diff below is a small cleanup to keep the accounting of events in
> sync with the number of events on the list. This is a noop for the
> moment, but it's small & easy part to review of my upcoming diff.
>
> ok?
OK bluhm@
>
> Index: kern/kern_event.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_event.c,v
> retrieving revision 1.79
> diff -u -p -r1.79 kern_event.c
> --- kern/kern_event.c 31 May 2017 14:52:05 -0000 1.79
> +++ kern/kern_event.c 9 Oct 2017 09:57:54 -0000
> @@ -760,22 +760,24 @@ start:
> TAILQ_INSERT_TAIL(&kq->kq_head, &marker, kn_tqe);
> while (count) {
> kn = TAILQ_FIRST(&kq->kq_head);
> - TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
> if (kn == &marker) {
> + TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
> splx(s);
> if (count == maxevents)
> goto retry;
> goto done;
> }
> +
> + TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
> + kq->kq_count--;
> +
> if (kn->kn_status & KN_DISABLED) {
> kn->kn_status &= ~KN_QUEUED;
> - kq->kq_count--;
> continue;
> }
> if ((kn->kn_flags & EV_ONESHOT) == 0 &&
> kn->kn_fop->f_event(kn, 0) == 0) {
> kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
> - kq->kq_count--;
> continue;
> }
> *kevp = kn->kn_kevent;
> @@ -783,7 +785,6 @@ start:
> nkev++;
> if (kn->kn_flags & EV_ONESHOT) {
> kn->kn_status &= ~KN_QUEUED;
> - kq->kq_count--;
> splx(s);
> kn->kn_fop->f_detach(kn);
> knote_drop(kn, p, p->p_fd);
> @@ -796,9 +797,9 @@ start:
> if (kn->kn_flags & EV_DISPATCH)
> kn->kn_status |= KN_DISABLED;
> kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
> - kq->kq_count--;
> } else {
> TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
> + kq->kq_count++;
> }
> count--;
> if (nkev == KQ_NEVENTS) {
