Release 4.7 include/linux/kref.h
/*
* 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/bug.h>
#include <linux/atomic.h>
#include <linux/kernel.h>
#include <linux/mutex.h>
struct kref {
atomic_t refcount;
};
/**
* kref_init - initialize object.
* @kref: object in question.
*/
static inline void kref_init(struct kref *kref)
{
atomic_set(&kref->refcount, 1);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| peter zijlstra | peter zijlstra | 14 | 63.64% | 1 | 50.00% |
| greg kroah-hartman | greg kroah-hartman | 8 | 36.36% | 1 | 50.00% |
| Total | 22 | 100.00% | 2 | 100.00% |
/**
* kref_get - increment refcount for object.
* @kref: object.
*/
static inline void kref_get(struct kref *kref)
{
/* If refcount was 0 before incrementing then we have a race
* condition when this kref is freeing by some other thread right now.
* In this case one should use kref_get_unless_zero()
*/
WARN_ON_ONCE(atomic_inc_return(&kref->refcount) < 2);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| peter zijlstra | peter zijlstra | 13 | 50.00% | 1 | 25.00% |
| greg kroah-hartman | greg kroah-hartman | 8 | 30.77% | 2 | 50.00% |
| anatol pomozov | anatol pomozov | 5 | 19.23% | 1 | 25.00% |
| Total | 26 | 100.00% | 4 | 100.00% |
/**
* kref_sub - subtract a number of refcounts for object.
* @kref: object.
* @count: Number of recounts to subtract.
* @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.
*
* Subtract @count from 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_sub(struct kref *kref, unsigned int count,
void (*release)(struct kref *kref))
{
WARN_ON(release == NULL);
if (atomic_sub_and_test((int) count, &kref->refcount)) {
release(kref);
return 1;
}
return 0;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| peter zijlstra | peter zijlstra | 44 | 69.84% | 2 | 40.00% |
| greg kroah-hartman | greg kroah-hartman | 19 | 30.16% | 3 | 60.00% |
| Total | 63 | 100.00% | 5 | 100.00% |
/**
* 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))
{
return kref_sub(kref, 1, release);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| thomas hellstrom | thomas hellstrom | 19 | 55.88% | 1 | 33.33% |
| peter zijlstra | peter zijlstra | 15 | 44.12% | 2 | 66.67% |
| Total | 34 | 100.00% | 3 | 100.00% |
static inline int kref_put_mutex(struct kref *kref,
void (*release)(struct kref *kref),
struct mutex *lock)
{
WARN_ON(release == NULL);
if (unlikely(!atomic_add_unless(&kref->refcount, -1, 1))) {
mutex_lock(lock);
if (unlikely(!atomic_dec_and_test(&kref->refcount))) {
mutex_unlock(lock);
return 0;
}
release(kref);
return 1;
}
return 0;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| al viro | al viro | 97 | 100.00% | 1 | 100.00% |
| Total | 97 | 100.00% | 1 | 100.00% |
/**
* 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 atomic_add_unless(&kref->refcount, 1, 0);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| thomas hellstrom | thomas hellstrom | 26 | 100.00% | 1 | 100.00% |
| Total | 26 | 100.00% | 1 | 100.00% |
#endif /* _KREF_H_ */
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| al viro | al viro | 100 | 33.00% | 1 | 7.14% |
| peter zijlstra | peter zijlstra | 90 | 29.70% | 2 | 14.29% |
| greg kroah-hartman | greg kroah-hartman | 56 | 18.48% | 5 | 35.71% |
| thomas hellstrom | thomas hellstrom | 46 | 15.18% | 2 | 14.29% |
| anatol pomozov | anatol pomozov | 5 | 1.65% | 1 | 7.14% |
| james bottomley | james bottomley | 3 | 0.99% | 1 | 7.14% |
| linus torvalds | linus torvalds | 2 | 0.66% | 1 | 7.14% |
| robert p. j. day | robert p. j. day | 1 | 0.33% | 1 | 7.14% |
| Total | 303 | 100.00% | 14 | 100.00% |
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