cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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kref.h (3155B)

      1/* SPDX-License-Identifier: GPL-2.0-only */
      2/*
      3 * kref.h - library routines for handling generic reference counted objects
      4 *
      5 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
      6 * Copyright (C) 2004 IBM Corp.
      7 *
      8 * based on kobject.h which was:
      9 * Copyright (C) 2002-2003 Patrick Mochel <mochel@osdl.org>
     10 * Copyright (C) 2002-2003 Open Source Development Labs
     11 */
     12
     13#ifndef _KREF_H_
     14#define _KREF_H_
     15
     16#include <linux/spinlock.h>
     17#include <linux/refcount.h>
     18
     19struct kref {
     20	refcount_t refcount;
     21};
     22
     23#define KREF_INIT(n)	{ .refcount = REFCOUNT_INIT(n), }
     24
     25/**
     26 * kref_init - initialize object.
     27 * @kref: object in question.
     28 */
     29static inline void kref_init(struct kref *kref)
     30{
     31	refcount_set(&kref->refcount, 1);
     32}
     33
     34static inline unsigned int kref_read(const struct kref *kref)
     35{
     36	return refcount_read(&kref->refcount);
     37}
     38
     39/**
     40 * kref_get - increment refcount for object.
     41 * @kref: object.
     42 */
     43static inline void kref_get(struct kref *kref)
     44{
     45	refcount_inc(&kref->refcount);
     46}
     47
     48/**
     49 * kref_put - decrement refcount for object.
     50 * @kref: object.
     51 * @release: pointer to the function that will clean up the object when the
     52 *	     last reference to the object is released.
     53 *	     This pointer is required, and it is not acceptable to pass kfree
     54 *	     in as this function.
     55 *
     56 * Decrement the refcount, and if 0, call release().
     57 * Return 1 if the object was removed, otherwise return 0.  Beware, if this
     58 * function returns 0, you still can not count on the kref from remaining in
     59 * memory.  Only use the return value if you want to see if the kref is now
     60 * gone, not present.
     61 */
     62static inline int kref_put(struct kref *kref, void (*release)(struct kref *kref))
     63{
     64	if (refcount_dec_and_test(&kref->refcount)) {
     65		release(kref);
     66		return 1;
     67	}
     68	return 0;
     69}
     70
     71static inline int kref_put_mutex(struct kref *kref,
     72				 void (*release)(struct kref *kref),
     73				 struct mutex *lock)
     74{
     75	if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) {
     76		release(kref);
     77		return 1;
     78	}
     79	return 0;
     80}
     81
     82static inline int kref_put_lock(struct kref *kref,
     83				void (*release)(struct kref *kref),
     84				spinlock_t *lock)
     85{
     86	if (refcount_dec_and_lock(&kref->refcount, lock)) {
     87		release(kref);
     88		return 1;
     89	}
     90	return 0;
     91}
     92
     93/**
     94 * kref_get_unless_zero - Increment refcount for object unless it is zero.
     95 * @kref: object.
     96 *
     97 * Return non-zero if the increment succeeded. Otherwise return 0.
     98 *
     99 * This function is intended to simplify locking around refcounting for
    100 * objects that can be looked up from a lookup structure, and which are
    101 * removed from that lookup structure in the object destructor.
    102 * Operations on such objects require at least a read lock around
    103 * lookup + kref_get, and a write lock around kref_put + remove from lookup
    104 * structure. Furthermore, RCU implementations become extremely tricky.
    105 * With a lookup followed by a kref_get_unless_zero *with return value check*
    106 * locking in the kref_put path can be deferred to the actual removal from
    107 * the lookup structure and RCU lookups become trivial.
    108 */
    109static inline int __must_check kref_get_unless_zero(struct kref *kref)
    110{
    111	return refcount_inc_not_zero(&kref->refcount);
    112}
    113#endif /* _KREF_H_ */