From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- include/linux/kref.h | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) create mode 100644 include/linux/kref.h (limited to 'include/linux/kref.h') diff --git a/include/linux/kref.h b/include/linux/kref.h new file mode 100644 index 000000000..d32e21a25 --- /dev/null +++ b/include/linux/kref.h @@ -0,0 +1,113 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * kref.h - library routines for handling generic reference counted objects + * + * Copyright (C) 2004 Greg Kroah-Hartman + * Copyright (C) 2004 IBM Corp. + * + * based on kobject.h which was: + * Copyright (C) 2002-2003 Patrick Mochel + * Copyright (C) 2002-2003 Open Source Development Labs + */ + +#ifndef _KREF_H_ +#define _KREF_H_ + +#include +#include + +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. + * This pointer is required, and it is not acceptable to pass kfree + * in as this 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. + */ +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; +} + +static inline int kref_put_mutex(struct kref *kref, + void (*release)(struct kref *kref), + struct mutex *lock) +{ + if (refcount_dec_and_mutex_lock(&kref->refcount, lock)) { + release(kref); + return 1; + } + return 0; +} + +static inline int kref_put_lock(struct kref *kref, + void (*release)(struct kref *kref), + spinlock_t *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. + * + * 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. + * 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. + */ +static inline int __must_check kref_get_unless_zero(struct kref *kref) +{ + return refcount_inc_not_zero(&kref->refcount); +} +#endif /* _KREF_H_ */ -- cgit v1.2.3