On 30/11/20(Mon) 17:23, Martin Pieuchot wrote:
> On 30/11/20(Mon) 17:06, Visa Hankala wrote:
> > On Mon, Nov 30, 2020 at 01:28:14PM -0300, Martin Pieuchot wrote:
> > > I plan to commit this in 3 steps, to ease a possible revert:
> > > - kevent(2) refactoring
> > > - introduction of newer kq* APIs
> > > - dopselect rewrite
> >
> > Please send a separate patch for the first step.
>
> Here's it. Diff below changes kevent(2) to possibly call kqueue_scan()
> multiple times. The same pattern is/will be used by select(2) and
> poll(2).
>
> The copyout(2) and ktrace entry point have been moved to the syscall
> function.
visa@ noticed that clearing the timeout was redundant with the element
check in kqueue_scan() so move the comment there.
Comments? Oks?
Index: kern/kern_event.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_event.c,v
retrieving revision 1.145
diff -u -p -r1.145 kern_event.c
--- kern/kern_event.c 25 Nov 2020 13:49:00 -0000 1.145
+++ kern/kern_event.c 1 Dec 2020 17:20:57 -0000
@@ -567,6 +567,7 @@ sys_kevent(struct proc *p, void *v, regi
struct timespec ts;
struct timespec *tsp = NULL;
int i, n, nerrors, error;
+ int ready, total;
struct kevent kev[KQ_NEVENTS];
if ((fp = fd_getfile(fdp, SCARG(uap, fd))) == NULL)
@@ -595,9 +596,9 @@ sys_kevent(struct proc *p, void *v, regi
kq = fp->f_data;
nerrors = 0;
- while (SCARG(uap, nchanges) > 0) {
- n = SCARG(uap, nchanges) > KQ_NEVENTS ?
- KQ_NEVENTS : SCARG(uap, nchanges);
+ while ((n = SCARG(uap, nchanges)) > 0) {
+ if (n > nitems(kev))
+ n = nitems(kev);
error = copyin(SCARG(uap, changelist), kev,
n * sizeof(struct kevent));
if (error)
@@ -635,11 +636,30 @@ sys_kevent(struct proc *p, void *v, regi
kqueue_scan_setup(&scan, kq);
FRELE(fp, p);
- error = kqueue_scan(&scan, SCARG(uap, nevents), SCARG(uap, eventlist),
- tsp, kev, p, &n);
+ /*
+ * Collect as many events as we can. The timeout on successive
+ * loops is disabled (kqueue_scan() becomes non-blocking).
+ */
+ total = 0;
+ error = 0;
+ while ((n = SCARG(uap, nevents) - total) > 0) {
+ if (n > nitems(kev))
+ n = nitems(kev);
+ ready = kqueue_scan(&scan, n, kev, tsp, p, &error);
+ if (ready == 0)
+ break;
+ error = copyout(kev, SCARG(uap, eventlist) + total,
+ sizeof(struct kevent) * ready);
+#ifdef KTRACE
+ if (KTRPOINT(p, KTR_STRUCT))
+ ktrevent(p, kev, ready);
+#endif
+ total += ready;
+ if (error || ready < n)
+ break;
+ }
kqueue_scan_finish(&scan);
-
- *retval = n;
+ *retval = total;
return (error);
done:
@@ -893,22 +913,22 @@ kqueue_sleep(struct kqueue *kq, struct t
return (error);
}
+/*
+ * Scan the kqueue, blocking if necessary until the target time is reached.
+ * If tsp is NULL we block indefinitely. If tsp->ts_secs/nsecs are both
+ * 0 we do not block at all.
+ */
int
kqueue_scan(struct kqueue_scan_state *scan, int maxevents,
- struct kevent *ulistp, struct timespec *tsp, struct kevent *kev,
- struct proc *p, int *retval)
+ struct kevent *kevp, struct timespec *tsp, struct proc *p, int *errorp)
{
struct kqueue *kq = scan->kqs_kq;
- struct kevent *kevp;
struct knote *kn;
- int s, count, nkev, error = 0;
+ int s, count, nkev = 0, error = 0;
- nkev = 0;
- kevp = kev;
count = maxevents;
if (count == 0)
goto done;
-
retry:
KASSERT(count == maxevents);
KASSERT(nkev == 0);
@@ -920,6 +940,10 @@ retry:
s = splhigh();
if (kq->kq_count == 0) {
+ /*
+ * Successive loops are only necessary if there are more
+ * ready events to gather, so they don't need to block.
+ */
if ((tsp != NULL && !timespecisset(tsp)) ||
scan->kqs_nevent != 0) {
splx(s);
@@ -958,14 +982,8 @@ retry:
while (count) {
kn = TAILQ_NEXT(&scan->kqs_start, kn_tqe);
if (kn->kn_filter == EVFILT_MARKER) {
- if (kn == &scan->kqs_end) {
- TAILQ_REMOVE(&kq->kq_head, &scan->kqs_start,
- kn_tqe);
- splx(s);
- if (scan->kqs_nevent == 0)
- goto retry;
- goto done;
- }
+ if (kn == &scan->kqs_end)
+ break;
/* Move start marker past another thread's marker. */
TAILQ_REMOVE(&kq->kq_head, &scan->kqs_start, kn_tqe);
@@ -1001,6 +1019,9 @@ retry:
count--;
scan->kqs_nevent++;
+ /*
+ * Post-event action on the note
+ */
if (kn->kn_flags & EV_ONESHOT) {
splx(s);
kn->kn_fop->f_detach(kn);
@@ -1026,35 +1047,14 @@ retry:
knote_release(kn);
}
kqueue_check(kq);
- if (nkev == KQ_NEVENTS) {
- splx(s);
-#ifdef KTRACE
- if (KTRPOINT(p, KTR_STRUCT))
- ktrevent(p, kev, nkev);
-#endif
- error = copyout(kev, ulistp,
- sizeof(struct kevent) * nkev);
- ulistp += nkev;
- nkev = 0;
- kevp = kev;
- s = splhigh();
- if (error)
- break;
- }
}
TAILQ_REMOVE(&kq->kq_head, &scan->kqs_start, kn_tqe);
splx(s);
+ if (scan->kqs_nevent == 0)
+ goto retry;
done:
- if (nkev != 0) {
-#ifdef KTRACE
- if (KTRPOINT(p, KTR_STRUCT))
- ktrevent(p, kev, nkev);
-#endif
- error = copyout(kev, ulistp,
- sizeof(struct kevent) * nkev);
- }
- *retval = maxevents - count;
- return (error);
+ *errorp = error;
+ return (nkev);
}
void
Index: sys/event.h
===================================================================
RCS file: /cvs/src/sys/sys/event.h,v
retrieving revision 1.47
diff -u -p -r1.47 event.h
--- sys/event.h 25 Nov 2020 13:49:00 -0000 1.47
+++ sys/event.h 1 Dec 2020 17:20:09 -0000
@@ -223,7 +223,7 @@ extern void knote_processexit(struct pro
extern int kqueue_register(struct kqueue *kq,
struct kevent *kev, struct proc *p);
extern int kqueue_scan(struct kqueue_scan_state *, int, struct kevent *,
- struct timespec *, struct kevent *, struct proc *, int *);
+ struct timespec *, struct proc *, int *);
extern void kqueue_scan_setup(struct kqueue_scan_state *, struct kqueue *);
extern void kqueue_scan_finish(struct kqueue_scan_state *);
extern int filt_seltrue(struct knote *kn, long hint);
