On 21/12/20(Mon) 16:45, Visa Hankala wrote:
> There is a slight inconsistency in klist_invalidate(). If the knote is
> already in the event queue and has flag EV_ONESHOT, kqueue_scan() will
> not invoke the newly set f_event. In this case, the kevent(2) system
> call will return the knote's original event state that no longer
> reflects the state that is reachable through the file descriptor
> (the caller of klist_invalidate() has already revoked access to the
> file or device).
I don't understand the problem. Why should filt_dead() be called? Is
it a race between two threads? Would you mind giving a scenario or some
code example?
> I think a proper fix is to invoke f_event manually to force the state
> update.
>
> OK?
>
> Index: kern/kern_event.c
> ===================================================================
> RCS file: src/sys/kern/kern_event.c,v
> retrieving revision 1.153
> diff -u -p -r1.153 kern_event.c
> --- kern/kern_event.c 20 Dec 2020 12:54:05 -0000 1.153
> +++ kern/kern_event.c 21 Dec 2020 16:19:30 -0000
> @@ -1618,6 +1618,7 @@ klist_invalidate(struct klist *list)
> kn->kn_fop->f_detach(kn);
> if (kn->kn_fop->f_flags & FILTEROP_ISFD) {
> kn->kn_fop = &dead_filtops;
> + kn->kn_fop->f_event(kn, 0);
> knote_activate(kn);
> s = splhigh();
> knote_release(kn);
>
