include/linux/kref.h

Source file repositories/reference/linux-study-clean/include/linux/kref.h

File Facts

System
Linux kernel
Corpus path
include/linux/kref.h
Extension
.h
Size
3991 bytes
Lines
136
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

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)) {

Annotation

Implementation Notes