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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136/* SPDX-License-Identifier: GPL-2.0-only *//* * 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 */
#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. * * Decrement the refcount, and if 0, call @release. The caller may not * pass NULL or kfree() as the release function. * * Return: 1 if this call removed the object, otherwise return 0. Beware, * if this function returns 0, another caller may have removed the object * by the time this function returns. The return value is only certain * if you want to see if the object is definitely released. */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;}
/** * kref_put_mutex - 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. * @mutex: Mutex which protects the release function. * * This variant of kref_lock() calls the @release function with the @mutex * held. The @release function will release the mutex. */static inline int kref_put_mutex(struct kref *kref, void (*release)(struct kref *kref), struct mutex *mutex) __cond_acquires(true, mutex){ if (refcount_dec_and_mutex_lock(&kref->refcount, mutex)) { release(kref); return 1; } return 0;}
/** * kref_put_lock - 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. * @lock: Spinlock which protects the release function. * * This variant of kref_lock() calls the @release function with the @lock * held. The @release function will release the lock. */static inline int kref_put_lock(struct kref *kref, void (*release)(struct kref *kref), spinlock_t *lock) __cond_acquires(true, 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. * * 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. * * Return: non-zero if the increment succeeded. Otherwise return 0. */static inline int __must_check kref_get_unless_zero(struct kref *kref){ return refcount_inc_not_zero(&kref->refcount);}#endif /* _KREF_H_ */