On Wed, May 31, 2017 at 08:37 +0200, Jan Schreiber wrote:
> Hi,
>
> I recently stumbled upon software that relies on EV_RECEIPT and
> EV_DISPATCH to be available as flags. It also showed up as dependency
> for a Rust crate.
> FreeBSD has it since 8.1 and OSX since 10.5.
> Patch is below.
>
> mike@ looked throug, thanks a lot!
>
That was me (mikeb@).
> Jan
>
> Index: sys/kern/kern_event.c
> ===================================================================
> RCS file: /cvs/src/sys/kern/kern_event.c,v
> retrieving revision 1.78
> diff -u -p -u -r1.78 kern_event.c
> --- sys/kern/kern_event.c 11 Feb 2017 19:51:06 -0000 1.78
> +++ sys/kern/kern_event.c 30 May 2017 22:38:49 -0000
> @@ -512,7 +512,7 @@ sys_kevent(struct proc *p, void *v, regi
> kevp = &kq->kq_kev[i];
> kevp->flags &= ~EV_SYSFLAGS;
> error = kqueue_register(kq, kevp, p);
> - if (error) {
> + if (error || (kevp->flags & EV_RECEIPT)) {
> if (SCARG(uap, nevents) != 0) {
> kevp->flags = EV_ERROR;
> kevp->data = error;
> @@ -788,9 +788,13 @@ start:
> kn->kn_fop->f_detach(kn);
> knote_drop(kn, p, p->p_fd);
> s = splhigh();
> - } else if (kn->kn_flags & EV_CLEAR) {
> - kn->kn_data = 0;
> - kn->kn_fflags = 0;
> + } else if (kn->kn_flags & (EV_CLEAR | EV_DISPATCH)) {
> + if (kn->kn_flags & EV_CLEAR) {
> + kn->kn_data = 0;
> + kn->kn_fflags = 0;
> + }
> + if (kn->kn_flags & EV_DISPATCH)
> + kn->kn_status |= KN_DISABLED;
> kn->kn_status &= ~(KN_QUEUED | KN_ACTIVE);
> kq->kq_count--;
> } else {
> Index: sys/sys/event.h
> ===================================================================
> RCS file: /cvs/src/sys/sys/event.h,v
> retrieving revision 1.23
> diff -u -p -u -r1.23 event.h
> --- sys/sys/event.h 24 Sep 2016 18:39:17 -0000 1.23
> +++ sys/sys/event.h 30 May 2017 22:31:04 -0000
> @@ -68,6 +68,8 @@ struct kevent {
> /* flags */
> #define EV_ONESHOT 0x0010 /* only report one occurrence */
> #define EV_CLEAR 0x0020 /* clear event state after reporting */
> +#define EV_RECEIPT 0x0040 /* force EV_ERROR on success, data=0 */
> +#define EV_DISPATCH 0x0080 /* disable event after reporting */
>
> #define EV_SYSFLAGS 0xF000 /* reserved by system */
> #define EV_FLAG1 0x2000 /* filter-specific flag */
> Index: lib/libc/sys/kqueue.2
> ===================================================================
> RCS file: /cvs/src/lib/libc/sys/kqueue.2,v
> retrieving revision 1.33
> diff -u -p -u -r1.33 kqueue.2
> --- lib/libc/sys/kqueue.2 13 Aug 2016 17:05:02 -0000 1.33
> +++ lib/libc/sys/kqueue.2 30 May 2017 22:30:29 -0000
> @@ -184,10 +184,25 @@ Disable the event so
> .Fn kevent
> will not return it.
> The filter itself is not disabled.
> +.It Dv EV_DISPATCH
> +Disable the event source immediately after delivery of an event.
> +See
> +.Dv EV_DISABLE
> +above.
> .It Dv EV_DELETE
> Removes the event from the kqueue.
> Events which are attached to file descriptors are automatically deleted
> on the last close of the descriptor.
> +.It Dv EV_RECEIPT
> +Causes
> +.Fn kevent
> +to return with
> +.Dv EV_ERROR
> +set without draining any pending events after updating events in the kqueue.
> +When a filter is successfully added the
> +.Va data
> +field will be zero.
> +This flag is useful for making bulk changes to a kqueue.
> .It Dv EV_ONESHOT
> Causes the event to return only the first occurrence of the filter
> being triggered.
>
We've tweaked the description for EV_RECEIPT a bit because FreeBSD
version didn't make a whole lot sense.
