1#ifndef __LINUX_LOCKREF_H
 2#define __LINUX_LOCKREF_H
 3
 4/*
 5 * Locked reference counts.
 6 *
 7 * These are different from just plain atomic refcounts in that they
 8 * are atomic with respect to the spinlock that goes with them.  In
 9 * particular, there can be implementations that don't actually get
10 * the spinlock for the common decrement/increment operations, but they
11 * still have to check that the operation is done semantically as if
12 * the spinlock had been taken (using a cmpxchg operation that covers
13 * both the lock and the count word, or using memory transactions, for
14 * example).
15 */
16
17#include <linux/spinlock.h>
18#include <generated/bounds.h>
19
20#define USE_CMPXCHG_LOCKREF \
21	(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
22	 IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
23
24struct lockref {
25	union {
26#if USE_CMPXCHG_LOCKREF
27		aligned_u64 lock_count;
28#endif
29		struct {
30			spinlock_t lock;
31			int count;
32		};
33	};
34};
35
36extern void lockref_get(struct lockref *);
37extern int lockref_put_return(struct lockref *);
38extern int lockref_get_not_zero(struct lockref *);
39extern int lockref_get_or_lock(struct lockref *);
40extern int lockref_put_or_lock(struct lockref *);
41
42extern void lockref_mark_dead(struct lockref *);
43extern int lockref_get_not_dead(struct lockref *);
44
45/* Must be called under spinlock for reliable results */
46static inline int __lockref_is_dead(const struct lockref *l)
47{
48	return ((int)l->count < 0);
49}
50
51#endif /* __LINUX_LOCKREF_H */

 1/* SPDX-License-Identifier: GPL-2.0 */
 2#ifndef __LINUX_LOCKREF_H
 3#define __LINUX_LOCKREF_H
 4
 5/*
 6 * Locked reference counts.
 7 *
 8 * These are different from just plain atomic refcounts in that they
 9 * are atomic with respect to the spinlock that goes with them.  In
10 * particular, there can be implementations that don't actually get
11 * the spinlock for the common decrement/increment operations, but they
12 * still have to check that the operation is done semantically as if
13 * the spinlock had been taken (using a cmpxchg operation that covers
14 * both the lock and the count word, or using memory transactions, for
15 * example).
16 */
17
18#include <linux/spinlock.h>
19#include <generated/bounds.h>
20
21#define USE_CMPXCHG_LOCKREF \
22	(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
23	 IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
24
25struct lockref {
26	union {
27#if USE_CMPXCHG_LOCKREF
28		aligned_u64 lock_count;
29#endif
30		struct {
31			spinlock_t lock;
32			int count;
33		};
34	};
35};
36
37extern void lockref_get(struct lockref *);
38extern int lockref_put_return(struct lockref *);
39extern int lockref_get_not_zero(struct lockref *);
40extern int lockref_put_not_zero(struct lockref *);
41extern int lockref_put_or_lock(struct lockref *);
42
43extern void lockref_mark_dead(struct lockref *);
44extern int lockref_get_not_dead(struct lockref *);
45
46/* Must be called under spinlock for reliable results */
47static inline bool __lockref_is_dead(const struct lockref *l)
48{
49	return ((int)l->count < 0);
50}
51
52#endif /* __LINUX_LOCKREF_H */