diff options
Diffstat (limited to 'include/linux/kref.h')
| -rw-r--r-- | include/linux/kref.h | 140 |
1 files changed, 51 insertions, 89 deletions
diff --git a/include/linux/kref.h b/include/linux/kref.h index 484604d184be..88e82ab1367c 100644 --- a/include/linux/kref.h +++ b/include/linux/kref.h @@ -1,3 +1,4 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ /* * kref.h - library routines for handling generic reference counted objects * @@ -7,31 +8,32 @@ * 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> #include <linux/spinlock.h> +#include <linux/refcount.h> struct kref { - atomic_t refcount; + 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) { - atomic_set(&kref->refcount, 1); + refcount_set(&kref->refcount, 1); +} + +static inline unsigned int kref_read(const struct kref *kref) +{ + return refcount_read(&kref->refcount); } /** @@ -40,37 +42,26 @@ static inline void kref_init(struct kref *kref) */ 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); + refcount_inc(&kref->refcount); } /** - * 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 + * 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. * - * 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. + * 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_sub(struct kref *kref, unsigned int count, - void (*release)(struct kref *kref)) +static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref)) { - WARN_ON(release == NULL); - - if (atomic_sub_and_test((int) count, &kref->refcount)) { + if (refcount_dec_and_test(&kref->refcount)) { release(kref); return 1; } @@ -78,70 +69,41 @@ static inline int kref_sub(struct kref *kref, unsigned int count, } /** - * kref_put - decrement refcount for object. - * @kref: object. - * @release: pointer to the function that will clean up the object when the + * 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. - * 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. + * @mutex: Mutex which protects the release function. * - * 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. + * 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(struct kref *kref, void (*release)(struct kref *kref)) -{ - return kref_sub(kref, 1, release); -} - -/** - * kref_put_spinlock_irqsave - 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. - * @lock: lock to take in release case - * - * Behaves identical to kref_put with one exception. If the reference count - * drops to zero, the lock will be taken atomically wrt dropping the reference - * count. The release function has to call spin_unlock() without _irqrestore. - */ -static inline int kref_put_spinlock_irqsave(struct kref *kref, - void (*release)(struct kref *kref), - spinlock_t *lock) +static inline int kref_put_mutex(struct kref *kref, + void (*release)(struct kref *kref), + struct mutex *mutex) { - unsigned long flags; - - WARN_ON(release == NULL); - if (atomic_add_unless(&kref->refcount, -1, 1)) - return 0; - spin_lock_irqsave(lock, flags); - if (atomic_dec_and_test(&kref->refcount)) { + if (refcount_dec_and_mutex_lock(&kref->refcount, mutex)) { release(kref); - local_irq_restore(flags); return 1; } - spin_unlock_irqrestore(lock, flags); return 0; } -static inline int kref_put_mutex(struct kref *kref, - void (*release)(struct kref *kref), - struct mutex *lock) +/** + * 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) { - 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; - } + if (refcount_dec_and_lock(&kref->refcount, lock)) { release(kref); return 1; } @@ -152,8 +114,6 @@ static inline int kref_put_mutex(struct kref *kref, * 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. @@ -163,9 +123,11 @@ static inline int kref_put_mutex(struct kref *kref, * 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 atomic_add_unless(&kref->refcount, 1, 0); + return refcount_inc_not_zero(&kref->refcount); } #endif /* _KREF_H_ */ |