linux-kernel - [PATCH 4/7] kref: Remove WARN_ON for NULL release functions

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Message-Id: <20170315021431.13107-5-andi@firstfloor.org>
Date:   Tue, 14 Mar 2017 19:14:28 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        gregkh@...uxfoundation.org, peterz@...radead.org
Subject: [PATCH 4/7] kref: Remove WARN_ON for NULL release functions

From: Andi Kleen <ak@...ux.intel.com>

The kref functions check for NULL release functions.
This WARN_ON seems rather pointless. We will eventually release and
then just crash nicely. It is also somewhat expensive because
these functions are inlined in a lot of places.
Removing the WARN_ONs saves around 2.3k in this kernel
(likely more in others with more drivers)

   text    data     bss     dec     hex filename
9083992 5367600 11116544        25568136        1862388 vmlinux-before-load-avg
9070166 5367600 11116544        25554310        185ed86 vmlinux-load-avg

Cc: gregkh@...uxfoundation.org
Cc: peterz@...radead.org
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 include/linux/kref.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/include/linux/kref.h b/include/linux/kref.h
index f4156f88f557..29220724bf1c 100644
--- a/include/linux/kref.h
+++ b/include/linux/kref.h
@@ -66,8 +66,6 @@ static inline void kref_get(struct kref *kref)
  */
 static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
 {
-	WARN_ON(release == NULL);
-
 	if (refcount_dec_and_test(&kref->refcount)) {
 		release(kref);
 		return 1;
@@ -79,8 +77,6 @@ static inline int kref_put_mutex(struct kref *kref,
 				 void (*release)(struct kref *kref),
 				 struct mutex *lock)
 {
-	WARN_ON(release == NULL);
-
 	if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) {
 		release(kref);
 		return 1;
@@ -92,8 +88,6 @@ static inline int kref_put_lock(struct kref *kref,
 				void (*release)(struct kref *kref),
 				spinlock_t *lock)
 {
-	WARN_ON(release == NULL);
-
 	if (refcount_dec_and_lock(&kref->refcount, lock)) {
 		release(kref);
 		return 1;
-- 
2.9.3