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, 2 insertions, 4 deletions

diff --git a/sys/kern/sys_pipe.c b/sys/kern/sys_pipe.c
index f4adfcb..45dc0f6 100644
--- a/sys/kern/sys_pipe.c
+++ b/sys/kern/sys_pipe.c
@@ -328,10 +328,8 @@ kern_pipe(struct thread *td, int fildes[2])
 	rpipe = &pp->pp_rpipe;
 	wpipe = &pp->pp_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);
+	knlist_init_mtx(&rpipe->pipe_sel.si_note, PIPE_MTX(rpipe));
+	knlist_init_mtx(&wpipe->pipe_sel.si_note, PIPE_MTX(wpipe));
 
 	/* Only the forward direction pipe is backed by default */
 	if ((error = pipe_create(rpipe, 1)) != 0 ||