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Date:      Mon, 8 May 2017 21:08:39 +0000 (UTC)
From:      Marius Strobl <marius@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r317982 - in head/sys: kern sys
Message-ID:  <201705082108.v48L8dV7053453@repo.freebsd.org>
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Author: marius
Date: Mon May  8 21:08:39 2017
New Revision: 317982
URL: https://svnweb.freebsd.org/changeset/base/317982

Log:
  - 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.

Modified:
  head/sys/kern/subr_kobj.c
  head/sys/sys/kobj.h

Modified: head/sys/kern/subr_kobj.c
==============================================================================
--- head/sys/kern/subr_kobj.c	Mon May  8 20:58:32 2017	(r317981)
+++ head/sys/kern/subr_kobj.c	Mon May  8 21:08:39 2017	(r317982)
@@ -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;
 }
 

Modified: head/sys/sys/kobj.h
==============================================================================
--- head/sys/sys/kobj.h	Mon May  8 20:58:32 2017	(r317981)
+++ head/sys/sys/kobj.h	Mon May  8 21:08:39 2017	(r317982)
@@ -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

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