Fix the recent panics/LORs/hangs created by my kqueue commit by:

- Introducing the possibility of using locks different than mutexes
for the knlist locking. In order to do this, we add three arguments to
knlist_init() to specify the functions to use to lock, unlock and
check if the lock is owned. If these arguments are NULL, we assume
mtx_lock, mtx_unlock and mtx_owned, respectively.

- Using the vnode lock for the knlist locking, when doing kqueue operations
on a vnode. This way, we don't have to lock the vnode while holding a
mutex, in filt_vfsread.

Reviewed by:	jmg
Approved by:	re (scottl), scottl (mentor override)
Pointyhat to:	ssouhlal
Will be happy:	everyone

16 files changed, 176 insertions, 75 deletions

diff --git a/sys/cam/scsi/scsi_target.c b/sys/cam/scsi/scsi_target.c
index b60c805..0b7caac 100644
--- a/sys/cam/scsi/scsi_target.c
+++ b/sys/cam/scsi/scsi_target.c
@@ -196,7 +196,7 @@ targopen(struct cdev *dev, int flags, int fmt, struct thread *td)
 	TAILQ_INIT(&softc->work_queue);
 	TAILQ_INIT(&softc->abort_queue);
 	TAILQ_INIT(&softc->user_ccb_queue);
-	knlist_init(&softc->read_select.si_note, &softc->mtx);
+	knlist_init(&softc->read_select.si_note, &softc->mtx, NULL, NULL, NULL);
 
 	return (0);
 }
diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 8c9f7ff..1b35665 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -368,7 +368,7 @@ proc0_init(void *dummy __unused)
 	p->p_flag = P_SYSTEM;
 	p->p_sflag = PS_INMEM;
 	p->p_state = PRS_NORMAL;
-	knlist_init(&p->p_klist, &p->p_mtx);
+	knlist_init(&p->p_klist, &p->p_mtx, NULL, NULL, NULL);
 	p->p_nice = NZERO;
 	td->td_state = TDS_RUNNING;
 	kg->kg_pri_class = PRI_TIMESHARE;
diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index d9ec1fd..2e71f23 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -185,12 +185,31 @@ SYSCTL_INT(_kern, OID_AUTO, kq_calloutmax, CTLFLAG_RW,
 } while (0)
 #define KN_LIST_LOCK(kn) do {						\
 	if (kn->kn_knlist != NULL)					\
-		mtx_lock(kn->kn_knlist->kl_lock);			\
+		kn->kn_knlist->kl_lock(kn->kn_knlist->kl_lockarg);	\
 } while (0)
 #define KN_LIST_UNLOCK(kn) do {						\
-	if (kn->kn_knlist != NULL)					\
-		mtx_unlock(kn->kn_knlist->kl_lock);			\
+	if (kn->kn_knlist != NULL) 					\
+		kn->kn_knlist->kl_unlock(kn->kn_knlist->kl_lockarg);	\
+} while (0)
+#define	KNL_ASSERT_LOCK(knl, islocked) do {				\
+	if (islocked)							\
+		KNL_ASSERT_LOCKED(knl);				\
+	else								\
+		KNL_ASSERT_UNLOCKED(knl);				\
 } while (0)
+#ifdef INVARIANTS
+#define	KNL_ASSERT_LOCKED(knl) do {					\
+	if (!knl->kl_locked((knl)->kl_lockarg))				\
+			panic("knlist not locked, but should be");	\
+} while (0)
+#define	KNL_ASSERT_UNLOCKED(knl) do {				\
+	if (knl->kl_locked((knl)->kl_lockarg))				\
+		panic("knlist locked, but should not be");		\
+} while (0)
+#else /* !INVARIANTS */
+#define	KNL_ASSERT_LOCKED(knl) do {} while(0)
+#define	KNL_ASSERT_UNLOCKED(knl) do {} while (0)
+#endif /* INVARIANTS */
 
 #define	KN_HASHSIZE		64		/* XXX should be tunable */
 #define KN_HASH(val, mask)	(((val) ^ (val >> 8)) & (mask))
@@ -499,7 +518,7 @@ kqueue(struct thread *td, struct kqueue_args *uap)
 	mtx_init(&kq->kq_lock, "kqueue", NULL, MTX_DEF|MTX_DUPOK);
 	TAILQ_INIT(&kq->kq_head);
 	kq->kq_fdp = fdp;
-	knlist_init(&kq->kq_sel.si_note, &kq->kq_lock);
+	knlist_init(&kq->kq_sel.si_note, &kq->kq_lock, NULL, NULL, NULL);
 	TASK_INIT(&kq->kq_task, 0, kqueue_task, kq);
 
 	FILEDESC_LOCK_FAST(fdp);
@@ -1507,9 +1526,11 @@ knote(struct knlist *list, long hint, int islocked)
 	if (list == NULL)
 		return;
 
-	mtx_assert(list->kl_lock, islocked ? MA_OWNED : MA_NOTOWNED);
-	if (!islocked)
-		mtx_lock(list->kl_lock);
+	KNL_ASSERT_LOCK(list, islocked);
+
+	if (!islocked) 
+		list->kl_lock(list->kl_lockarg); 
+
 	/*
 	 * If we unlock the list lock (and set KN_INFLUX), we can eliminate
 	 * the kqueue scheduling, but this will introduce four
@@ -1533,7 +1554,7 @@ knote(struct knlist *list, long hint, int islocked)
 		kq = NULL;
 	}
 	if (!islocked)
-		mtx_unlock(list->kl_lock);
+		list->kl_unlock(list->kl_lockarg); 
 }
 
 /*
@@ -1542,15 +1563,15 @@ knote(struct knlist *list, long hint, int islocked)
 void
 knlist_add(struct knlist *knl, struct knote *kn, int islocked)
 {
-	mtx_assert(knl->kl_lock, islocked ? MA_OWNED : MA_NOTOWNED);
+	KNL_ASSERT_LOCK(knl, islocked);
 	KQ_NOTOWNED(kn->kn_kq);
 	KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) ==
 	    (KN_INFLUX|KN_DETACHED), ("knote not KN_INFLUX and KN_DETACHED"));
 	if (!islocked)
-		mtx_lock(knl->kl_lock);
+		knl->kl_lock(knl->kl_lockarg);
 	SLIST_INSERT_HEAD(&knl->kl_list, kn, kn_selnext);
 	if (!islocked)
-		mtx_unlock(knl->kl_lock);
+		knl->kl_unlock(knl->kl_lockarg);
 	KQ_LOCK(kn->kn_kq);
 	kn->kn_knlist = knl;
 	kn->kn_status &= ~KN_DETACHED;
@@ -1561,17 +1582,17 @@ static void
 knlist_remove_kq(struct knlist *knl, struct knote *kn, int knlislocked, int kqislocked)
 {
 	KASSERT(!(!!kqislocked && !knlislocked), ("kq locked w/o knl locked"));
-	mtx_assert(knl->kl_lock, knlislocked ? MA_OWNED : MA_NOTOWNED);
+	KNL_ASSERT_LOCK(knl, knlislocked);
 	mtx_assert(&kn->kn_kq->kq_lock, kqislocked ? MA_OWNED : MA_NOTOWNED);
 	if (!kqislocked)
 		KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) == KN_INFLUX,
     ("knlist_remove called w/o knote being KN_INFLUX or already removed"));
 	if (!knlislocked)
-		mtx_lock(knl->kl_lock);
+		knl->kl_lock(knl->kl_lockarg);
 	SLIST_REMOVE(&knl->kl_list, kn, knote, kn_selnext);
 	kn->kn_knlist = NULL;
 	if (!knlislocked)
-		mtx_unlock(knl->kl_lock);
+		knl->kl_unlock(knl->kl_lockarg);
 	if (!kqislocked)
 		KQ_LOCK(kn->kn_kq);
 	kn->kn_status |= KN_DETACHED;
@@ -1603,23 +1624,57 @@ knlist_remove_inevent(struct knlist *knl, struct knote *kn)
 int
 knlist_empty(struct knlist *knl)
 {
-
-	mtx_assert(knl->kl_lock, MA_OWNED);
+	KNL_ASSERT_LOCKED(knl);
 	return SLIST_EMPTY(&knl->kl_list);
 }
 
 static struct mtx	knlist_lock;
 MTX_SYSINIT(knlist_lock, &knlist_lock, "knlist lock for lockless objects",
 	MTX_DEF);
+static void knlist_mtx_lock(void *arg);
+static void knlist_mtx_unlock(void *arg);
+static int knlist_mtx_locked(void *arg);
+
+static void
+knlist_mtx_lock(void *arg)
+{
+	mtx_lock((struct mtx *)arg);
+}
+
+static void
+knlist_mtx_unlock(void *arg)
+{
+	mtx_unlock((struct mtx *)arg);
+}
+
+static int
+knlist_mtx_locked(void *arg)
+{
+	return (mtx_owned((struct mtx *)arg));
+}
 
 void
-knlist_init(struct knlist *knl, struct mtx *mtx)
+knlist_init(struct knlist *knl, void *lock, void (*kl_lock)(void *),
+    void (*kl_unlock)(void *), int (*kl_locked)(void *))
 {
 
-	if (mtx == NULL)
-		knl->kl_lock = &knlist_lock;
+	if (lock == NULL)
+		knl->kl_lockarg = &knlist_lock;
+	else
+		knl->kl_lockarg = lock;
+
+	if (kl_lock == NULL)
+		knl->kl_lock = knlist_mtx_lock;
+	else
+		knl->kl_lock = kl_lock;
+	if (kl_lock == NULL)
+		knl->kl_unlock = knlist_mtx_unlock;
+	else
+		knl->kl_unlock = kl_unlock;
+	if (kl_locked == NULL)
+		knl->kl_locked = knlist_mtx_locked;
 	else
-		knl->kl_lock = mtx;
+		knl->kl_locked = kl_locked;
 
 	SLIST_INIT(&knl->kl_list);
 }
@@ -1637,7 +1692,7 @@ knlist_destroy(struct knlist *knl)
 		printf("WARNING: destroying knlist w/ knotes on it!\n");
 #endif
 
-	knl->kl_lock = NULL;
+	knl->kl_lockarg = knl->kl_lock = knl->kl_unlock = NULL;
 	SLIST_INIT(&knl->kl_list);
 }
 
@@ -1652,11 +1707,11 @@ knlist_cleardel(struct knlist *knl, struct thread *td, int islocked, int killkn)
 	struct kqueue *kq;
 
 	if (islocked)
-		mtx_assert(knl->kl_lock, MA_OWNED);
+		KNL_ASSERT_LOCKED(knl);
 	else {
-		mtx_assert(knl->kl_lock, MA_NOTOWNED);
+		KNL_ASSERT_UNLOCKED(knl);
 again:		/* need to reaquire lock since we have dropped it */
-		mtx_lock(knl->kl_lock);
+		knl->kl_lock(knl->kl_lockarg);
 	}
 
 	SLIST_FOREACH(kn, &knl->kl_list, kn_selnext) {
@@ -1686,7 +1741,7 @@ again:		/* need to reaquire lock since we have dropped it */
 		KQ_LOCK(kq);
 		KASSERT(kn->kn_status & KN_INFLUX,
 		    ("knote removed w/o list lock"));
-		mtx_unlock(knl->kl_lock);
+		knl->kl_unlock(knl->kl_lockarg);
 		kq->kq_state |= KQ_FLUXWAIT;
 		msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqkclr", 0);
 		kq = NULL;
@@ -1694,10 +1749,10 @@ again:		/* need to reaquire lock since we have dropped it */
 	}
 
 	if (islocked)
-		mtx_assert(knl->kl_lock, MA_OWNED);
+		KNL_ASSERT_LOCKED(knl);
 	else {
-		mtx_unlock(knl->kl_lock);
-		mtx_assert(knl->kl_lock, MA_NOTOWNED);
+		knl->kl_unlock(knl->kl_lockarg);
+		KNL_ASSERT_UNLOCKED(knl);
 	}
 }
 
diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 7521449..56ad939 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -271,7 +271,7 @@ fork1(td, flags, pages, procp)
 #ifdef MAC
 	mac_init_proc(newproc);
 #endif
-	knlist_init(&newproc->p_klist, &newproc->p_mtx);
+	knlist_init(&newproc->p_klist, &newproc->p_mtx, NULL, NULL, NULL);
 
 	/* We have to lock the process tree while we look for a pid. */
 	sx_slock(&proctree_lock);
diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index 267670c..d79a319 100644
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -351,8 +351,10 @@ pipe(td, uap)
 	rpipe = &pp->pp_rpipe;
 	wpipe = &pp->pp_wpipe;
 
-	knlist_init(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
-	knlist_init(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
+	knlist_init(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe), NULL, NULL,
+	    NULL);
+	knlist_init(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe), NULL, NULL,
+	    NULL);
 
 	/* Only the forward direction pipe is backed by default */
 	if (pipe_create(rpipe, 1) || pipe_create(wpipe, 0)) {
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 8a6585b..6263432 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -2865,8 +2865,8 @@ ttymalloc(struct tty *tp)
 	mtx_lock(&tty_list_mutex);
 	TAILQ_INSERT_TAIL(&tty_list, tp, t_list);
 	mtx_unlock(&tty_list_mutex);
-	knlist_init(&tp->t_rsel.si_note, &tp->t_mtx);
-	knlist_init(&tp->t_wsel.si_note, &tp->t_mtx);
+	knlist_init(&tp->t_rsel.si_note, &tp->t_mtx, NULL, NULL, NULL);
+	knlist_init(&tp->t_wsel.si_note, &tp->t_mtx, NULL, NULL, NULL);
 	return (tp);
 }
 
diff --git a/sys/kern/uipc_sockbuf.c b/sys/kern/uipc_sockbuf.c
index cb1a24c..e979251 100644
--- a/sys/kern/uipc_sockbuf.c
+++ b/sys/kern/uipc_sockbuf.c
@@ -235,8 +235,10 @@ sonewconn(head, connstatus)
 	mac_create_socket_from_socket(head, so);
 	SOCK_UNLOCK(head);
 #endif
-	knlist_init(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv));
-	knlist_init(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd));
+	knlist_init(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv),
+	    NULL, NULL, NULL);
+	knlist_init(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd),
+	    NULL, NULL, NULL);
 	if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat) ||
 	    (*so->so_proto->pr_usrreqs->pru_attach)(so, 0, NULL)) {
 		sodealloc(so);
diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index 7ffc1c4..c776c0c 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -211,8 +211,10 @@ socreate(dom, aso, type, proto, cred, td)
 #ifdef MAC
 	mac_create_socket(cred, so);
 #endif
-	knlist_init(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv));
-	knlist_init(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd));
+	knlist_init(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv),
+	    NULL, NULL, NULL);
+	knlist_init(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd),
+	    NULL, NULL, NULL);
 	so->so_count = 1;
 	error = (*prp->pr_usrreqs->pru_attach)(so, proto, td);
 	if (error) {
diff --git a/sys/kern/uipc_socket2.c b/sys/kern/uipc_socket2.c
index cb1a24c..e979251 100644
--- a/sys/kern/uipc_socket2.c
+++ b/sys/kern/uipc_socket2.c
@@ -235,8 +235,10 @@ sonewconn(head, connstatus)
 	mac_create_socket_from_socket(head, so);
 	SOCK_UNLOCK(head);
 #endif
-	knlist_init(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv));
-	knlist_init(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd));
+	knlist_init(&so->so_rcv.sb_sel.si_note, SOCKBUF_MTX(&so->so_rcv),
+	    NULL, NULL, NULL);
+	knlist_init(&so->so_snd.sb_sel.si_note, SOCKBUF_MTX(&so->so_snd),
+	    NULL, NULL, NULL);
 	if (soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat) ||
 	    (*so->so_proto->pr_usrreqs->pru_attach)(so, 0, NULL)) {
 		sodealloc(so);
diff --git a/sys/kern/vfs_aio.c b/sys/kern/vfs_aio.c
index 7cae398..87ab064 100644
--- a/sys/kern/vfs_aio.c
+++ b/sys/kern/vfs_aio.c
@@ -1287,7 +1287,7 @@ _aio_aqueue(struct thread *td, struct aiocb *job, struct aio_liojob *lj, int typ
 	aiocbe->inputcharge = 0;
 	aiocbe->outputcharge = 0;
 	/* XXX - need a lock */
-	knlist_init(&aiocbe->klist, NULL);
+	knlist_init(&aiocbe->klist, NULL, NULL, NULL, NULL);
 
 	suword(&job->_aiocb_private.status, -1);
 	suword(&job->_aiocb_private.error, 0);
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 1697696..92cb025 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -98,6 +98,10 @@ static void	vfree(struct vnode *);
 static void	vnlru_free(int);
 static void	vdestroy(struct vnode *);
 static void	vgonel(struct vnode *);
+static void	vfs_knllock(void *arg);
+static void	vfs_knlunlock(void *arg);
+static int	vfs_knllocked(void *arg);
+
 
 /*
  * Enable Giant pushdown based on whether or not the vm is mpsafe in this
@@ -2834,8 +2838,8 @@ v_addpollinfo(struct vnode *vp)
 	}
 	vp->v_pollinfo = vi;
 	mtx_init(&vp->v_pollinfo->vpi_lock, "vnode pollinfo", NULL, MTX_DEF);
-	knlist_init(&vp->v_pollinfo->vpi_selinfo.si_note,
-	    &vp->v_pollinfo->vpi_lock);
+	knlist_init(&vp->v_pollinfo->vpi_selinfo.si_note, vp, vfs_knllock,
+	    vfs_knlunlock, vfs_knllocked);
 }
 
 /*
@@ -3473,7 +3477,7 @@ vop_create_post(void *ap, int rc)
 	struct vop_create_args *a = ap;
 
 	if (!rc)
-		VFS_SEND_KNOTE(a->a_dvp, NOTE_WRITE);
+		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE); 
 }
 
 void
@@ -3482,8 +3486,8 @@ vop_link_post(void *ap, int rc)
 	struct vop_link_args *a = ap;
 	
 	if (!rc) {
-		VFS_SEND_KNOTE(a->a_vp, NOTE_LINK);
-		VFS_SEND_KNOTE(a->a_tdvp, NOTE_WRITE);
+		VFS_KNOTE_LOCKED(a->a_vp, NOTE_LINK); 
+		VFS_KNOTE_LOCKED(a->a_tdvp, NOTE_WRITE);
 	}
 }
 
@@ -3493,7 +3497,7 @@ vop_mkdir_post(void *ap, int rc)
 	struct vop_mkdir_args *a = ap;
 
 	if (!rc)
-		VFS_SEND_KNOTE(a->a_dvp, NOTE_WRITE | NOTE_LINK);
+		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE | NOTE_LINK);
 }
 
 void
@@ -3502,7 +3506,7 @@ vop_mknod_post(void *ap, int rc)
 	struct vop_mknod_args *a = ap;
 
 	if (!rc)
-		VFS_SEND_KNOTE(a->a_dvp, NOTE_WRITE);
+		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
 }
 
 void
@@ -3511,8 +3515,8 @@ vop_remove_post(void *ap, int rc)
 	struct vop_remove_args *a = ap;
 
 	if (!rc) {
-		VFS_SEND_KNOTE(a->a_dvp, NOTE_WRITE);
-		VFS_SEND_KNOTE(a->a_vp, NOTE_DELETE);
+		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
+		VFS_KNOTE_LOCKED(a->a_vp, NOTE_DELETE);
 	}
 }
 
@@ -3522,11 +3526,11 @@ vop_rename_post(void *ap, int rc)
 	struct vop_rename_args *a = ap;
 
 	if (!rc) {
-		VFS_SEND_KNOTE(a->a_fdvp, NOTE_WRITE);
-		VFS_SEND_KNOTE(a->a_tdvp, NOTE_WRITE);
-		VFS_SEND_KNOTE(a->a_fvp, NOTE_RENAME);
+		VFS_KNOTE_UNLOCKED(a->a_fdvp, NOTE_WRITE);
+		VFS_KNOTE_UNLOCKED(a->a_tdvp, NOTE_WRITE);
+		VFS_KNOTE_UNLOCKED(a->a_fvp, NOTE_RENAME);
 		if (a->a_tvp)
-			VFS_SEND_KNOTE(a->a_tvp, NOTE_DELETE);
+			VFS_KNOTE_UNLOCKED(a->a_tvp, NOTE_DELETE);
 	}
 	if (a->a_tdvp != a->a_fdvp)
 		vdrop(a->a_fdvp);
@@ -3543,8 +3547,8 @@ vop_rmdir_post(void *ap, int rc)
 	struct vop_rmdir_args *a = ap;
 
 	if (!rc) {
-		VFS_SEND_KNOTE(a->a_dvp, NOTE_WRITE | NOTE_LINK);
-		VFS_SEND_KNOTE(a->a_vp, NOTE_DELETE);
+		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE | NOTE_LINK);
+		VFS_KNOTE_LOCKED(a->a_vp, NOTE_DELETE);
 	}
 }
 
@@ -3554,7 +3558,7 @@ vop_setattr_post(void *ap, int rc)
 	struct vop_setattr_args *a = ap;
 
 	if (!rc)
-		VFS_SEND_KNOTE(a->a_vp, NOTE_ATTRIB);
+		VFS_KNOTE_LOCKED(a->a_vp, NOTE_ATTRIB);
 }
 
 void
@@ -3563,7 +3567,7 @@ vop_symlink_post(void *ap, int rc)
 	struct vop_symlink_args *a = ap;
 	
 	if (!rc)
-		VFS_SEND_KNOTE(a->a_dvp, NOTE_WRITE);
+		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
 }
 
 static struct knlist fs_knlist;
@@ -3571,7 +3575,7 @@ static struct knlist fs_knlist;
 static void
 vfs_event_init(void *arg)
 {
-	knlist_init(&fs_knlist, NULL);
+	knlist_init(&fs_knlist, NULL, NULL, NULL, NULL);
 }
 /* XXX - correct order? */
 SYSINIT(vfs_knlist, SI_SUB_VFS, SI_ORDER_ANY, vfs_event_init, NULL);
@@ -3658,7 +3662,6 @@ static int	filt_vfsread(struct knote *kn, long hint);
 static int	filt_vfswrite(struct knote *kn, long hint);
 static int	filt_vfsvnode(struct knote *kn, long hint);
 static void	filt_vfsdetach(struct knote *kn);
-
 static struct filterops vfsread_filtops =
 	{ 1, NULL, filt_vfsdetach, filt_vfsread };
 static struct filterops vfswrite_filtops =
@@ -3666,11 +3669,36 @@ static struct filterops vfswrite_filtops =
 static struct filterops vfsvnode_filtops =
 	{ 1, NULL, filt_vfsdetach, filt_vfsvnode };
 
+static void
+vfs_knllock(void *arg)
+{
+	struct vnode *vp = arg;
+
+	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, curthread);
+}
+
+static void
+vfs_knlunlock(void *arg)
+{
+	struct vnode *vp = arg;
+
+	VOP_UNLOCK(vp, 0, curthread);
+}
+
+static int
+vfs_knllocked(void *arg)
+{
+	struct vnode *vp = arg;
+
+	return (VOP_ISLOCKED(vp, curthread) == LK_EXCLUSIVE);
+}
+
 int
 vfs_kqfilter(struct vop_kqfilter_args *ap)
 {
 	struct vnode *vp = ap->a_vp;
 	struct knote *kn = ap->a_kn;
+	struct knlist *knl; 
 
 	switch (kn->kn_filter) {
 	case EVFILT_READ:
@@ -3692,7 +3720,8 @@ vfs_kqfilter(struct vop_kqfilter_args *ap)
 		v_addpollinfo(vp);
 	if (vp->v_pollinfo == NULL)
 		return (ENOMEM);
-	knlist_add(&vp->v_pollinfo->vpi_selinfo.si_note, kn, 0);
+	knl = &vp->v_pollinfo->vpi_selinfo.si_note;
+	knlist_add(knl, kn, 0);
 
 	return (0);
 }
@@ -3725,11 +3754,8 @@ filt_vfsread(struct knote *kn, long hint)
 		return (1);
 	}
 
-	vn_lock(vp, LK_SHARED | LK_RETRY, curthread);
 	if (VOP_GETATTR(vp, &va, curthread->td_ucred, curthread)) 
 		return (0);
-	if (VOP_UNLOCK(vp, 0, curthread))
-		return (0);
 
 	kn->kn_data = va.va_size - kn->kn_fp->f_offset;
 	return (kn->kn_data != 0);
diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index 514d6d2..e917866 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -375,7 +375,7 @@ bpfopen(dev, flags, fmt, td)
 #endif
 	mtx_init(&d->bd_mtx, devtoname(dev), "bpf cdev lock", MTX_DEF);
 	callout_init(&d->bd_callout, NET_CALLOUT_MPSAFE);
-	knlist_init(&d->bd_sel.si_note, &d->bd_mtx);
+	knlist_init(&d->bd_sel.si_note, &d->bd_mtx, NULL, NULL, NULL);
 
 	return (0);
 }
diff --git a/sys/net/if.c b/sys/net/if.c
index e0285af..12090df 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -279,7 +279,7 @@ if_init(void *dummy __unused)
 
 	IFNET_LOCK_INIT();
 	TAILQ_INIT(&ifnet);
-	knlist_init(&ifklist, NULL);
+	knlist_init(&ifklist, NULL, NULL, NULL, NULL);
 	if_grow();				/* create initial table */
 	ifdev_byindex(0) = make_dev(&net_cdevsw, 0,
 	    UID_ROOT, GID_WHEEL, 0600, "network");
@@ -473,7 +473,7 @@ if_attach(struct ifnet *ifp)
 	TAILQ_INIT(&ifp->if_addrhead);
 	TAILQ_INIT(&ifp->if_prefixhead);
 	TAILQ_INIT(&ifp->if_multiaddrs);
-	knlist_init(&ifp->if_klist, NULL);
+	knlist_init(&ifp->if_klist, NULL, NULL, NULL, NULL);
 	getmicrotime(&ifp->if_lastchange);
 	ifp->if_data.ifi_epoch = time_uptime;
 	ifp->if_data.ifi_datalen = sizeof(struct if_data);
diff --git a/sys/sys/event.h b/sys/sys/event.h
index 82764bc..c2921c4 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -126,8 +126,11 @@ SLIST_HEAD(klist, knote);
 struct kqueue;
 SLIST_HEAD(kqlist, kqueue);
 struct knlist {
-	struct	mtx	*kl_lock;	/* lock to protect kll_list */
 	struct	klist	kl_list;
+	void    (*kl_lock)(void *);	/* lock function */
+	void    (*kl_unlock)(void *);
+	int    (*kl_locked)(void *);
+	void *kl_lockarg;		/* argument passed to kl_lockf() */
 };
 
 
@@ -209,7 +212,9 @@ extern void	knlist_add(struct knlist *knl, struct knote *kn, int islocked);
 extern void	knlist_remove(struct knlist *knl, struct knote *kn, int islocked);
 extern void	knlist_remove_inevent(struct knlist *knl, struct knote *kn);
 extern int	knlist_empty(struct knlist *knl);
-extern void	knlist_init(struct knlist *knl, struct mtx *mtx);
+extern void	knlist_init(struct knlist *knl, void *lock,
+    void (*kl_lock)(void *), void (*kl_unlock)(void *),
+    int (*kl_locked)(void *));
 extern void	knlist_destroy(struct knlist *knl);
 extern void	knlist_cleardel(struct knlist *knl, struct thread *td,
 	int islocked, int killkn);
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index 3ab383e..c70347c 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -550,11 +550,18 @@ extern int mpsafe_vfs;
 		mtx_assert(&Giant, MA_OWNED);				\
 } while (0)
 
-#define VFS_SEND_KNOTE(vp, hint) do					\
+#define VFS_KNOTE_LOCKED(vp, hint) do					\
 {									\
 	if ((vp)->v_mount &&						\
 	    ((vp)->v_mount->mnt_kern_flag & MNTK_NOKNOTE) == 0)		\
-		VN_KNOTE_UNLOCKED((vp), (hint));			\
+		VN_KNOTE((vp), (hint), 1);				\
+} while (0)
+
+#define VFS_KNOTE_UNLOCKED(vp, hint) do					\
+{									\
+	if ((vp)->v_mount &&						\
+	    ((vp)->v_mount->mnt_kern_flag & MNTK_NOKNOTE) == 0)		\
+		VN_KNOTE((vp), (hint), 0);				\
 } while (0)
 
 #include <sys/module.h>
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index b201f6d..2c9fd30 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -231,8 +231,8 @@ struct xvnode {
 		if (!VN_KNLIST_EMPTY(vp))			\
 			KNOTE(&vp->v_pollinfo->vpi_selinfo.si_note, (b), (a)); \
 	} while (0)
-#define VN_KNOTE_LOCKED(vp, b)		VN_KNOTE(vp, b, 1)
-#define VN_KNOTE_UNLOCKED(vp, b)	VN_KNOTE(vp, b, 0)
+#define	VN_KNOTE_UNLOCKED(vp, b)	VN_KNOTE(vp, b, 0)
+#define	VN_KNOTE_UNLOCKED(vp, b)	VN_KNOTE(vp, b, 0)
 
 /*
  * Vnode flags.
@@ -702,7 +702,7 @@ void	vop_unlock_pre(void *a);
 #define VOP_WRITE_POST(ap, ret)						\
 	noffset = (ap)->a_uio->uio_offset;				\
 	if (noffset > ooffset && !VN_KNLIST_EMPTY((ap)->a_vp)) {	\
-		VFS_SEND_KNOTE((ap)->a_vp, NOTE_WRITE			\
+		VFS_KNOTE_LOCKED((ap)->a_vp, NOTE_WRITE			\
 		    | (noffset > osize ? NOTE_EXTEND : 0));		\
 	}