Author: kib
Date: Sat Apr 12 14:09:35 2014
New Revision: 264369
URL: http://svnweb.freebsd.org/changeset/base/264369
Log:
MFC r264146:
Fix a race between kqueue_register() and kqueue_scan() setting KN_INFLUX
flag while knlist is not locked, which caused lost notifications from
parallel knote().
Modified:
stable/9/sys/kern/kern_event.c
stable/9/sys/sys/event.h
Directory Properties:
stable/9/sys/ (props changed)
stable/9/sys/sys/ (props changed)
Modified: stable/9/sys/kern/kern_event.c
==============================================================================
--- stable/9/sys/kern/kern_event.c Sat Apr 12 14:08:53 2014
(r264368)
+++ stable/9/sys/kern/kern_event.c Sat Apr 12 14:09:35 2014
(r264369)
@@ -465,7 +465,7 @@ knote_fork(struct knlist *list, int pid)
continue;
kq = kn->kn_kq;
KQ_LOCK(kq);
- if ((kn->kn_status & KN_INFLUX) == KN_INFLUX) {
+ if ((kn->kn_status & (KN_INFLUX | KN_SCAN)) == KN_INFLUX) {
KQ_UNLOCK(kq);
continue;
}
@@ -1129,7 +1129,7 @@ findkn:
* but doing so will not reset any filter which has already been
* triggered.
*/
- kn->kn_status |= KN_INFLUX;
+ kn->kn_status |= KN_INFLUX | KN_SCAN;
KQ_UNLOCK(kq);
KN_LIST_LOCK(kn);
kn->kn_kevent.udata = kev->udata;
@@ -1152,7 +1152,7 @@ done_ev_add:
KQ_LOCK(kq);
if (event)
KNOTE_ACTIVATE(kn, 1);
- kn->kn_status &= ~KN_INFLUX;
+ kn->kn_status &= ~(KN_INFLUX | KN_SCAN);
KN_LIST_UNLOCK(kn);
if ((kev->flags & EV_DISABLE) &&
@@ -1469,7 +1469,7 @@ start:
KQ_LOCK(kq);
kn = NULL;
} else {
- kn->kn_status |= KN_INFLUX;
+ kn->kn_status |= KN_INFLUX | KN_SCAN;
KQ_UNLOCK(kq);
if ((kn->kn_status & KN_KQUEUE) == KN_KQUEUE)
KQ_GLOBAL_LOCK(&kq_global, haskqglobal);
@@ -1478,7 +1478,8 @@ start:
KQ_LOCK(kq);
KQ_GLOBAL_UNLOCK(&kq_global, haskqglobal);
kn->kn_status &=
- ~(KN_QUEUED | KN_ACTIVE | KN_INFLUX);
+ ~(KN_QUEUED | KN_ACTIVE | KN_INFLUX |
+ KN_SCAN);
kq->kq_count--;
KN_LIST_UNLOCK(kn);
influx = 1;
@@ -1508,7 +1509,7 @@ start:
} else
TAILQ_INSERT_TAIL(&kq->kq_head, kn, kn_tqe);
- kn->kn_status &= ~(KN_INFLUX);
+ kn->kn_status &= ~(KN_INFLUX | KN_SCAN);
KN_LIST_UNLOCK(kn);
influx = 1;
}
@@ -1826,28 +1827,33 @@ knote(struct knlist *list, long hint, in
*/
SLIST_FOREACH(kn, &list->kl_list, kn_selnext) {
kq = kn->kn_kq;
- if ((kn->kn_status & KN_INFLUX) != KN_INFLUX) {
+ KQ_LOCK(kq);
+ if ((kn->kn_status & (KN_INFLUX | KN_SCAN)) == KN_INFLUX) {
+ /*
+ * Do not process the influx notes, except for
+ * the influx coming from the kq unlock in the
+ * kqueue_scan(). In the later case, we do
+ * not interfere with the scan, since the code
+ * fragment in kqueue_scan() locks the knlist,
+ * and cannot proceed until we finished.
+ */
+ KQ_UNLOCK(kq);
+ } else if ((lockflags & KNF_NOKQLOCK) != 0) {
+ kn->kn_status |= KN_INFLUX;
+ KQ_UNLOCK(kq);
+ error = kn->kn_fop->f_event(kn, hint);
KQ_LOCK(kq);
- if ((kn->kn_status & KN_INFLUX) == KN_INFLUX) {
- KQ_UNLOCK(kq);
- } else if ((lockflags & KNF_NOKQLOCK) != 0) {
- kn->kn_status |= KN_INFLUX;
- KQ_UNLOCK(kq);
- error = kn->kn_fop->f_event(kn, hint);
- KQ_LOCK(kq);
- kn->kn_status &= ~KN_INFLUX;
- if (error)
- KNOTE_ACTIVATE(kn, 1);
- KQ_UNLOCK_FLUX(kq);
- } else {
- kn->kn_status |= KN_HASKQLOCK;
- if (kn->kn_fop->f_event(kn, hint))
- KNOTE_ACTIVATE(kn, 1);
- kn->kn_status &= ~KN_HASKQLOCK;
- KQ_UNLOCK(kq);
- }
+ kn->kn_status &= ~KN_INFLUX;
+ if (error)
+ KNOTE_ACTIVATE(kn, 1);
+ KQ_UNLOCK_FLUX(kq);
+ } else {
+ kn->kn_status |= KN_HASKQLOCK;
+ if (kn->kn_fop->f_event(kn, hint))
+ KNOTE_ACTIVATE(kn, 1);
+ kn->kn_status &= ~KN_HASKQLOCK;
+ KQ_UNLOCK(kq);
}
- kq = NULL;
}
if ((lockflags & KNF_LISTLOCKED) == 0)
list->kl_unlock(list->kl_lockarg);
Modified: stable/9/sys/sys/event.h
==============================================================================
--- stable/9/sys/sys/event.h Sat Apr 12 14:08:53 2014 (r264368)
+++ stable/9/sys/sys/event.h Sat Apr 12 14:09:35 2014 (r264369)
@@ -210,6 +210,7 @@ struct knote {
#define KN_MARKER 0x20 /* ignore this knote */
#define KN_KQUEUE 0x40 /* this knote belongs to a kq */
#define KN_HASKQLOCK 0x80 /* for _inevent */
+#define KN_SCAN 0x100 /* flux set in
kqueue_scan() */
int kn_sfflags; /* saved filter flags */
intptr_t kn_sdata; /* saved data field */
union {
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