- Also outside of the KOBJOPLOOKUP macro - which in turn is used by

the code auto-generated for *.m - kobj_lookup_method(9) is useful;
  for example in back-ends or base class device drivers in order to
  determine whether a default method has been overridden. Thus, allow
  for the kobj_method_t pointer argument - used by KOBJOPLOOKUP in
  order to update the cache entry - of kobj_lookup_method(9), to be
  NULL. Actually, that pointer is redundant as it's just set to the
  same kobj_method_t that the kobj_lookup_method(9) function returns
  in the first place, but probably it serves to reduce the number of
  instructions generated for KOBJOPLOOKUP.
- For the same reason, move updating kobj_lookup_{hits,misses} (if
  KOBJ_STATS is defined) from kobj_lookup_method(9) to KOBJOPLOOKUP.
  As a side-effect, this gets rid of the convoluted approach of always
  incrementing kobj_lookup_hits in KOBJOPLOOKUP and then in case of
  a cache miss, decrementing it in kobj_lookup_method(9) again.

sys/kern/subr_kobj.c

@@ -213,19 +213,11 @@ kobj_lookup_method(kobj_class_t cls,
 {
 	kobj_method_t *ce;
 
-#ifdef KOBJ_STATS
-	/*
-	 * Correct for the 'hit' assumption in KOBJOPLOOKUP and record
-	 * a 'miss'.
-	 */
-	kobj_lookup_hits--;
-	kobj_lookup_misses++;
-#endif
-
 	ce = kobj_lookup_method_mi(cls, desc);
 	if (!ce)
 		ce = &desc->deflt;
-	*cep = ce;
+	if (cep)
+		*cep = ce;
 	return ce;
 }
 

sys/sys/kobj.h

@@ -226,10 +226,12 @@ extern u_int kobj_lookup_misses;
 	kobj_method_t **_cep =					\
 	    &OPS->cache[_desc->id & (KOBJ_CACHE_SIZE-1)];	\
 	kobj_method_t *_ce = *_cep;				\
-	kobj_lookup_hits++; /* assume hit */			\
-	if (_ce->desc != _desc)					\
+	if (_ce->desc != _desc) {				\
 		_ce = kobj_lookup_method(OPS->cls,		\
 					 _cep, _desc);		\
+		kobj_lookup_misses++;				\
+	} else							\
+		kobj_lookup_hits++;				\
 	_m = _ce->func;						\
 } while(0)
 #else