cregit-Linux how code gets into the kernel

Release 4.12 include/linux/kref.h

Directory: include/linux
 * kref.h - library routines for handling generic reference counted objects
 * Copyright (C) 2004 Greg Kroah-Hartman <>
 * Copyright (C) 2004 IBM Corp.
 * based on kobject.h which was:
 * Copyright (C) 2002-2003 Patrick Mochel <>
 * 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); }


Peter Zijlstra1463.64%266.67%
Greg Kroah-Hartman836.36%133.33%

static inline unsigned int kref_read(const struct kref *kref) { return refcount_read(&kref->refcount); }


Peter Zijlstra23100.00%2100.00%

/** * kref_get - increment refcount for object. * @kref: object. */
static inline void kref_get(struct kref *kref) { refcount_inc(&kref->refcount); }


Peter Zijlstra1260.00%250.00%
Greg Kroah-Hartman840.00%250.00%

/** * 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)) { if (refcount_dec_and_test(&kref->refcount)) { release(kref); return 1; } return 0; }


Peter Zijlstra2859.57%350.00%
Greg Kroah-Hartman1940.43%350.00%

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; }


Al Viro4074.07%133.33%
Peter Zijlstra1425.93%266.67%

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; }


Peter Zijlstra2954.72%266.67%
Al Viro2445.28%133.33%

/** * 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); }


Thomas Hellstrom2195.45%150.00%
Peter Zijlstra14.55%150.00%

#endif /* _KREF_H_ */

Overall Contributors

Peter Zijlstra13649.28%642.86%
Al Viro6423.19%17.14%
Greg Kroah-Hartman5118.48%428.57%
Thomas Hellstrom227.97%17.14%
Linus Torvalds20.72%17.14%
Robert P. J. Day10.36%17.14%
Directory: include/linux
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