Diff below changes the order of operations in kqueue_register() to get
rid of an unnecessary pool_get(). When an event is already present on
the list try to acquire it first. Note that knote_acquire() may sleep
in which case the list might have changed so the lookup has to always
begin from the start.
This will help with lazy removal of knote in poll/select. In this
scenario EV_ADD is generally always done with an knote already on the
list.
ok?
Index: kern/kern_event.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_event.c,v
retrieving revision 1.142
diff -u -p -r1.142 kern_event.c
--- kern/kern_event.c 12 Aug 2020 13:49:24 -0000 1.142
+++ kern/kern_event.c 18 Aug 2020 08:58:27 -0000
@@ -696,7 +696,7 @@ kqueue_register(struct kqueue *kq, struc
struct filedesc *fdp = kq->kq_fdp;
const struct filterops *fops = NULL;
struct file *fp = NULL;
- struct knote *kn = NULL, *newkn = NULL;
+ struct knote *kn, *newkn = NULL;
struct knlist *list = NULL;
int s, error = 0;
@@ -721,22 +721,12 @@ kqueue_register(struct kqueue *kq, struc
return (EBADF);
}
- if (kev->flags & EV_ADD)
- newkn = pool_get(&knote_pool, PR_WAITOK | PR_ZERO);
-
again:
+ kn = NULL;
if (fops->f_flags & FILTEROP_ISFD) {
- if ((fp = fd_getfile(fdp, kev->ident)) == NULL) {
- error = EBADF;
- goto done;
- }
- if (kev->flags & EV_ADD)
- kqueue_expand_list(kq, kev->ident);
if (kev->ident < kq->kq_knlistsize)
list = &kq->kq_knlist[kev->ident];
} else {
- if (kev->flags & EV_ADD)
- kqueue_expand_hash(kq);
if (kq->kq_knhashmask != 0) {
list = &kq->kq_knhash[
KN_HASH((u_long)kev->ident, kq->kq_knhashmask)];
@@ -749,10 +739,6 @@ again:
s = splhigh();
if (!knote_acquire(kn)) {
splx(s);
- if (fp != NULL) {
- FRELE(fp, p);
- fp = NULL;
- }
goto again;
}
splx(s);
@@ -760,6 +746,21 @@ again:
}
}
}
+
+ if (kev->flags & EV_ADD && kn == NULL) {
+ newkn = pool_get(&knote_pool, PR_WAITOK | PR_ZERO);
+ if (fops->f_flags & FILTEROP_ISFD) {
+ if ((fp = fd_getfile(fdp, kev->ident)) == NULL) {
+ error = EBADF;
+ goto done;
+ }
+ kqueue_expand_list(kq, kev->ident);
+ } else {
+ kqueue_expand_hash(kq);
+ }
+
+ }
+
KASSERT(kn == NULL || (kn->kn_status & KN_PROCESSING) != 0);
if (kn == NULL && ((kev->flags & EV_ADD) == 0)) {
