The previous change introducing the kqueue_scan_setup()/finish() API
required to switch poll(2) internals to use the kqueue mechanism has
been backed out. The reason for the regression is still unknown, so
let's take a baby step approach.
Diff below introduces the new API with only minimal changes. It should
not introduce any change in behavior.
Comments? Oks?
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 14 Aug 2020 10:13:38 -0000
@@ -64,9 +64,6 @@ void KQREF(struct kqueue *);
void KQRELE(struct kqueue *);
int kqueue_sleep(struct kqueue *, struct timespec *);
-int kqueue_scan(struct kqueue *kq, int maxevents,
- struct kevent *ulistp, struct timespec *timeout,
- struct kevent *kev, struct proc *p, int *retval);
int kqueue_read(struct file *, struct uio *, int);
int kqueue_write(struct file *, struct uio *, int);
@@ -554,6 +551,7 @@ out:
int
sys_kevent(struct proc *p, void *v, register_t *retval)
{
+ struct kqueue_scan_state scan;
struct filedesc* fdp = p->p_fd;
struct sys_kevent_args /* {
syscallarg(int) fd;
@@ -635,11 +633,12 @@ sys_kevent(struct proc *p, void *v, regi
goto done;
}
- KQREF(kq);
+ kqueue_scan_setup(&scan, kq);
FRELE(fp, p);
- error = kqueue_scan(kq, SCARG(uap, nevents), SCARG(uap, eventlist),
+ error = kqueue_scan(&scan, SCARG(uap, nevents), SCARG(uap, eventlist),
tsp, kev, p, &n);
- KQRELE(kq);
+ kqueue_scan_finish(&scan);
+
*retval = n;
return (error);
@@ -895,11 +894,13 @@ kqueue_sleep(struct kqueue *kq, struct t
}
int
-kqueue_scan(struct kqueue *kq, int maxevents, struct kevent *ulistp,
- struct timespec *tsp, struct kevent *kev, struct proc *p, int *retval)
+kqueue_scan(struct kqueue_scan_state *scan, int maxevents,
+ struct kevent *ulistp, struct timespec *tsp, struct kevent *kev,
+ struct proc *p, int *retval)
{
+ struct kqueue *kq = scan->kqs_kq;
struct kevent *kevp;
- struct knote mend, mstart, *kn;
+ struct knote *kn;
int s, count, nkev, error = 0;
nkev = 0;
@@ -909,9 +910,6 @@ kqueue_scan(struct kqueue *kq, int maxev
if (count == 0)
goto done;
- memset(&mstart, 0, sizeof(mstart));
- memset(&mend, 0, sizeof(mend));
-
retry:
KASSERT(count == maxevents);
KASSERT(nkev == 0);
@@ -939,18 +937,16 @@ retry:
goto done;
}
- mstart.kn_filter = EVFILT_MARKER;
- mstart.kn_status = KN_PROCESSING;
- TAILQ_INSERT_HEAD(&kq->kq_head, &mstart, kn_tqe);
- mend.kn_filter = EVFILT_MARKER;
- mend.kn_status = KN_PROCESSING;
- TAILQ_INSERT_TAIL(&kq->kq_head, &mend, kn_tqe);
+ TAILQ_INSERT_TAIL(&kq->kq_head, &scan->kqs_end, kn_tqe);
+ TAILQ_INSERT_HEAD(&kq->kq_head, &scan->kqs_start, kn_tqe);
while (count) {
- kn = TAILQ_NEXT(&mstart, kn_tqe);
+ kn = TAILQ_NEXT(&scan->kqs_start, kn_tqe);
if (kn->kn_filter == EVFILT_MARKER) {
- if (kn == &mend) {
- TAILQ_REMOVE(&kq->kq_head, &mend, kn_tqe);
- TAILQ_REMOVE(&kq->kq_head, &mstart, kn_tqe);
+ if (kn == &scan->kqs_end) {
+ TAILQ_REMOVE(&kq->kq_head, &scan->kqs_end,
+ kn_tqe);
+ TAILQ_REMOVE(&kq->kq_head, &scan->kqs_start,
+ kn_tqe);
splx(s);
if (count == maxevents)
goto retry;
@@ -958,8 +954,9 @@ retry:
}
/* Move start marker past another thread's marker. */
- TAILQ_REMOVE(&kq->kq_head, &mstart, kn_tqe);
- TAILQ_INSERT_AFTER(&kq->kq_head, kn, &mstart, kn_tqe);
+ TAILQ_REMOVE(&kq->kq_head, &scan->kqs_start, kn_tqe);
+ TAILQ_INSERT_AFTER(&kq->kq_head, kn, &scan->kqs_start,
+ kn_tqe);
continue;
}
@@ -1029,8 +1026,8 @@ retry:
break;
}
}
- TAILQ_REMOVE(&kq->kq_head, &mend, kn_tqe);
- TAILQ_REMOVE(&kq->kq_head, &mstart, kn_tqe);
+ TAILQ_REMOVE(&kq->kq_head, &scan->kqs_end, kn_tqe);
+ TAILQ_REMOVE(&kq->kq_head, &scan->kqs_start, kn_tqe);
splx(s);
done:
if (nkev != 0) {
@@ -1044,6 +1041,33 @@ done:
*retval = maxevents - count;
return (error);
}
+
+void
+kqueue_scan_setup(struct kqueue_scan_state *scan, struct kqueue *kq)
+{
+ memset(scan, 0, sizeof(*scan));
+
+ KQREF(kq);
+ scan->kqs_kq = kq;
+ scan->kqs_start.kn_filter = EVFILT_MARKER;
+ scan->kqs_start.kn_status = KN_PROCESSING;
+ scan->kqs_end.kn_filter = EVFILT_MARKER;
+ scan->kqs_end.kn_status = KN_PROCESSING;
+}
+
+void
+kqueue_scan_finish(struct kqueue_scan_state *scan)
+{
+ struct kqueue *kq = scan->kqs_kq;
+
+ KASSERT(scan->kqs_start.kn_filter == EVFILT_MARKER);
+ KASSERT(scan->kqs_start.kn_status == KN_PROCESSING);
+ KASSERT(scan->kqs_end.kn_filter == EVFILT_MARKER);
+ KASSERT(scan->kqs_end.kn_status == KN_PROCESSING);
+
+ KQRELE(kq);
+}
+
/*
* XXX
Index: sys/event.h
===================================================================
RCS file: /cvs/src/sys/sys/event.h,v
retrieving revision 1.44
diff -u -p -r1.44 event.h
--- sys/event.h 22 Jun 2020 13:14:32 -0000 1.44
+++ sys/event.h 14 Aug 2020 10:14:18 -0000
@@ -200,7 +200,14 @@ struct knote {
#define kn_fp kn_ptr.p_fp
};
+struct kqueue_scan_state {
+ struct kqueue *kqs_kq; /* kqueue of this scan */
+ struct knote kqs_start; /* start marker */
+ struct knote kqs_end; /* end marker */
+};
+
struct proc;
+struct timespec;
extern const struct filterops sig_filtops;
extern const struct filterops dead_filtops;
@@ -212,6 +219,10 @@ extern void knote_fdclose(struct proc *p
extern void knote_processexit(struct proc *);
extern int kqueue_register(struct kqueue *kq,
struct kevent *kev, struct proc *p);
+int kqueue_scan(struct kqueue_scan_state *, int, struct kevent *,
+ struct timespec *, struct kevent *, 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);
extern int seltrue_kqfilter(dev_t, struct knote *);
extern void klist_insert(struct klist *, struct knote *);
