The allproc lock is a sx lock, not a mutex, so fix the assertion. This

asserts that the sx lock is held, but does not specify if the lock is held
shared or exclusive, thus either type of lock satisfies the assertion.

sys/fs/pseudofs/pseudofs_vnops.c

@@ -543,7 +543,7 @@ static int
 pfs_iterate(struct thread *td, pid_t pid, struct pfs_node *pd,
 	    struct pfs_node **pn, struct proc **p)
 {
-	mtx_assert(&allproc, MA_OWNED);
+	sx_assert(&allproc, SX_LOCKED);
  again:
 	if (*pn == NULL) {
 		/* first node */