Adapt vfs kqfilter to the shared vnode lock used by zfs write vop. Use

vnode interlock to protect the knote fields [1]. The locking assumes
that shared vnode lock is held, thus we get exclusive access to knote
either by exclusive vnode lock protection, or by shared vnode lock +
vnode interlock.

Do not use kl_locked() method to assert either lock ownership or the
fact that curthread does not own the lock. For shared locks, ownership
is not recorded, e.g. VOP_ISLOCKED can return LK_SHARED for the shared
lock not owned by curthread, causing false positives in kqueue subsystem
assertions about knlist lock.

Remove kl_locked method from knlist lock vector, and add two separate
assertion methods kl_assert_locked and kl_assert_unlocked, that are
supposed to use proper asserts. Change knlist_init accordingly.

Add convenience function knlist_init_mtx to reduce number of arguments
for typical knlist initialization.

Submitted by:	jhb [1]
Noted by:	jhb [2]
Reviewed by:	jhb
Tested by:	rnoland

1 files changed, 5 insertions, 2 deletions

diff --git a/sys/sys/event.h b/sys/sys/event.h
index 37b0a77..824f084 100644
--- a/sys/sys/event.h
+++ b/sys/sys/event.h
@@ -124,7 +124,8 @@ struct knlist {
 	struct	klist	kl_list;
 	void    (*kl_lock)(void *);	/* lock function */
 	void    (*kl_unlock)(void *);
-	int    (*kl_locked)(void *);
+	void	(*kl_assert_locked)(void *);
+	void	(*kl_assert_unlocked)(void *);
 	void *kl_lockarg;		/* argument passed to kl_lockf() */
 };
 
@@ -203,6 +204,7 @@ struct kevent_copyops {
 struct thread;
 struct proc;
 struct knlist;
+struct mtx;
 
 extern void	knote(struct knlist *list, long hint, int islocked);
 extern void	knote_fork(struct knlist *list, int pid);
@@ -212,7 +214,8 @@ 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, void *lock,
     void (*kl_lock)(void *), void (*kl_unlock)(void *),
-    int (*kl_locked)(void *));
+    void (*kl_assert_locked)(void *), void (*kl_assert_unlocked)(void *));
+extern void	knlist_init_mtx(struct knlist *knl, struct mtx *lock);
 extern void	knlist_destroy(struct knlist *knl);
 extern void	knlist_cleardel(struct knlist *knl, struct thread *td,
 	int islocked, int killkn);