linux/lib/lockref.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/export.h>
#include <linux/lockref.h>

#if USE_CMPXCHG_LOCKREF

/*
 * Note that the "cmpxchg()" reloads the "old" value for the
 * failure case.
 */
#define CMPXCHG_LOOP …

#else

#define CMPXCHG_LOOP(CODE, SUCCESS) …

#endif

/**
 * lockref_get - Increments reference count unconditionally
 * @lockref: pointer to lockref structure
 *
 * This operation is only valid if you already hold a reference
 * to the object, so you know the count cannot be zero.
 */
void lockref_get(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);

/**
 * lockref_get_not_zero - Increments count unless the count is 0 or dead
 * @lockref: pointer to lockref structure
 * Return: 1 if count updated successfully or 0 if count was zero
 */
int lockref_get_not_zero(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);

/**
 * lockref_put_not_zero - Decrements count unless count <= 1 before decrement
 * @lockref: pointer to lockref structure
 * Return: 1 if count updated successfully or 0 if count would become zero
 */
int lockref_put_not_zero(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);

/**
 * lockref_put_return - Decrement reference count if possible
 * @lockref: pointer to lockref structure
 *
 * Decrement the reference count and return the new value.
 * If the lockref was dead or locked, return an error.
 */
int lockref_put_return(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);

/**
 * lockref_put_or_lock - decrements count unless count <= 1 before decrement
 * @lockref: pointer to lockref structure
 * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
 */
int lockref_put_or_lock(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);

/**
 * lockref_mark_dead - mark lockref dead
 * @lockref: pointer to lockref structure
 */
void lockref_mark_dead(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);

/**
 * lockref_get_not_dead - Increments count unless the ref is dead
 * @lockref: pointer to lockref structure
 * Return: 1 if count updated successfully or 0 if lockref was dead
 */
int lockref_get_not_dead(struct lockref *lockref)
{ … }
EXPORT_SYMBOL(…);