Re: Panic on kern_event.c

No issue using patched kernel on 2 servers (under stress test since +2
hours), Thanks !


Le mar. 20 nov. 2018 à 07:45, Mark Johnston <markj_at_freebsd.org> a écrit :

> On Mon, Nov 19, 2018 at 10:26:51AM +0100, Sylvain GALLIANO wrote:
> > With this latest patch, after stressing syslog-ng few minutes, it do not
> > log anymore and a simple kill do not work (I have to do kill -9)
>
> Thanks for your patience.  I finally managed to reproduce the problem
> and can see the bug now.  Please try this patch instead.
>
> diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
> index d9c670e29d60..0be765a040ed 100644
> --- a/sys/kern/kern_event.c
> +++ b/sys/kern/kern_event.c
> _at__at_ -1538,6 +1538,10 _at__at_ kqueue_register(struct kqueue *kq, struct kevent
> *kev, struct thread *td, int wa
>                         kn_enter_flux(kn);
>
>                         error = knote_attach(kn, kq);
> +                       if ((kev->flags & EV_ENABLE) != 0)
> +                               kn->kn_status &= ~KN_DISABLED;
> +                       else if ((kev->flags & EV_DISABLE) != 0)
> +                               kn->kn_status |= KN_DISABLED;
>                         KQ_UNLOCK(kq);
>                         if (error != 0) {
>                                 tkn = kn;
> _at__at_ -1570,6 +1574,11 _at__at_ kqueue_register(struct kqueue *kq, struct kevent
> *kev, struct thread *td, int wa
>                 KNOTE_ACTIVATE(kn, 1);
>         }
>
> +       if ((kev->flags & EV_ENABLE) != 0)
> +               kn->kn_status &= ~KN_DISABLED;
> +       else if ((kev->flags & EV_DISABLE) != 0)
> +               kn->kn_status |= KN_DISABLED;
> +
>         /*
>          * The user may change some filter values after the initial EV_ADD,
>          * but doing so will not reset any filter which has already been
> _at__at_ -1595,11 +1604,9 _at__at_ kqueue_register(struct kqueue *kq, struct kevent
> *kev, struct thread *td, int wa
>          * kn_knlist.
>          */
>  done_ev_add:
> -       if ((kev->flags & EV_ENABLE) != 0)
> -               kn->kn_status &= ~KN_DISABLED;
> -       else if ((kev->flags & EV_DISABLE) != 0)
> -               kn->kn_status |= KN_DISABLED;
> -
> +       /*
> +        * KN_DISABLED will be stable while the knote is in flux.
> +        */
>         if ((kn->kn_status & KN_DISABLED) == 0)
>                 event = kn->kn_fop->f_event(kn, 0);
>         else
> _at__at_ -1861,6 +1868,8 _at__at_ kqueue_scan(struct kqueue *kq, int maxevents, struct
> kevent_copyops *k_ops,
>                 }
>
>                 TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
> +               KASSERT(kn == marker || (kn->kn_status & KN_QUEUED) != 0,
> +                   ("knote %p not queued", kn));
>                 if ((kn->kn_status & KN_DISABLED) == KN_DISABLED) {
>                         kn->kn_status &= ~KN_QUEUED;
>                         kq->kq_count--;
>