mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-11-01 17:08:10 +00:00
ec48c940da
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
Link: http://lkml.kernel.org/r/20170315021431.13107-5-andi@firstfloor.org
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
118 lines
3.3 KiB
C
118 lines
3.3 KiB
C
/*
|
|
* kref.h - library routines for handling generic reference counted objects
|
|
*
|
|
* Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
|
|
* Copyright (C) 2004 IBM Corp.
|
|
*
|
|
* based on kobject.h which was:
|
|
* Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
|
|
* Copyright (C) 2002-2003 Open Source Development Labs
|
|
*
|
|
* This file is released under the GPLv2.
|
|
*
|
|
*/
|
|
|
|
#ifndef _KREF_H_
|
|
#define _KREF_H_
|
|
|
|
#include <linux/spinlock.h>
|
|
#include <linux/refcount.h>
|
|
|
|
struct kref {
|
|
refcount_t refcount;
|
|
};
|
|
|
|
#define KREF_INIT(n) { .refcount = REFCOUNT_INIT(n), }
|
|
|
|
/**
|
|
* kref_init - initialize object.
|
|
* @kref: object in question.
|
|
*/
|
|
static inline void kref_init(struct kref *kref)
|
|
{
|
|
refcount_set(&kref->refcount, 1);
|
|
}
|
|
|
|
static inline unsigned int kref_read(const struct kref *kref)
|
|
{
|
|
return refcount_read(&kref->refcount);
|
|
}
|
|
|
|
/**
|
|
* kref_get - increment refcount for object.
|
|
* @kref: object.
|
|
*/
|
|
static inline void kref_get(struct kref *kref)
|
|
{
|
|
refcount_inc(&kref->refcount);
|
|
}
|
|
|
|
/**
|
|
* kref_put - decrement refcount for object.
|
|
* @kref: object.
|
|
* @release: pointer to the function that will clean up the object when the
|
|
* last reference to the object is released.
|
|
* This pointer is required, and it is not acceptable to pass kfree
|
|
* in as this function. If the caller does pass kfree to this
|
|
* function, you will be publicly mocked mercilessly by the kref
|
|
* maintainer, and anyone else who happens to notice it. You have
|
|
* been warned.
|
|
*
|
|
* Decrement the refcount, and if 0, call release().
|
|
* Return 1 if the object was removed, otherwise return 0. Beware, if this
|
|
* function returns 0, you still can not count on the kref from remaining in
|
|
* memory. Only use the return value if you want to see if the kref is now
|
|
* gone, not present.
|
|
*/
|
|
static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
|
|
{
|
|
if (refcount_dec_and_test(&kref->refcount)) {
|
|
release(kref);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline int kref_put_mutex(struct kref *kref,
|
|
void (*release)(struct kref *kref),
|
|
struct mutex *lock)
|
|
{
|
|
if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) {
|
|
release(kref);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline int kref_put_lock(struct kref *kref,
|
|
void (*release)(struct kref *kref),
|
|
spinlock_t *lock)
|
|
{
|
|
if (refcount_dec_and_lock(&kref->refcount, lock)) {
|
|
release(kref);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* kref_get_unless_zero - Increment refcount for object unless it is zero.
|
|
* @kref: object.
|
|
*
|
|
* Return non-zero if the increment succeeded. Otherwise return 0.
|
|
*
|
|
* This function is intended to simplify locking around refcounting for
|
|
* objects that can be looked up from a lookup structure, and which are
|
|
* removed from that lookup structure in the object destructor.
|
|
* Operations on such objects require at least a read lock around
|
|
* lookup + kref_get, and a write lock around kref_put + remove from lookup
|
|
* structure. Furthermore, RCU implementations become extremely tricky.
|
|
* With a lookup followed by a kref_get_unless_zero *with return value check*
|
|
* locking in the kref_put path can be deferred to the actual removal from
|
|
* the lookup structure and RCU lookups become trivial.
|
|
*/
|
|
static inline int __must_check kref_get_unless_zero(struct kref *kref)
|
|
{
|
|
return refcount_inc_not_zero(&kref->refcount);
|
|
}
|
|
#endif /* _KREF_H_ */
|