[mirror_ubuntu-bionic-kernel.git] / include / linux / lockref.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_LOCKREF_H
#define __LINUX_LOCKREF_H

/*
 * Locked reference counts.
 *
 * These are different from just plain atomic refcounts in that they
 * are atomic with respect to the spinlock that goes with them.  In
 * particular, there can be implementations that don't actually get
 * the spinlock for the common decrement/increment operations, but they
 * still have to check that the operation is done semantically as if
 * the spinlock had been taken (using a cmpxchg operation that covers
 * both the lock and the count word, or using memory transactions, for
 * example).
 */

#include <linux/spinlock.h>
#include <generated/bounds.h>

#define USE_CMPXCHG_LOCKREF \
	(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
	 IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)

struct lockref {
	union {
#if USE_CMPXCHG_LOCKREF
		aligned_u64 lock_count;
#endif
		struct {
			spinlock_t lock;
			int count;
		};
	};
};

extern void lockref_get(struct lockref *);
extern int lockref_put_return(struct lockref *);
extern int lockref_get_not_zero(struct lockref *);
extern int lockref_get_or_lock(struct lockref *);
extern int lockref_put_or_lock(struct lockref *);

extern void lockref_mark_dead(struct lockref *);
extern int lockref_get_not_dead(struct lockref *);

/* Must be called under spinlock for reliable results */
static inline int __lockref_is_dead(const struct lockref *l)
{
	return ((int)l->count < 0);
}

#endif /* __LINUX_LOCKREF_H */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
0f8f2aaa WL	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>
57f4257e PZ	19	#include <generated/bounds.h>
	20
	21	#define USE_CMPXCHG_LOCKREF \
	22	(IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \
597d795a	23	IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4)
0f8f2aaa WL	24
0f8f2aaa WL	25	struct lockref {
bc08b449	26	union {
57f4257e	27	#if USE_CMPXCHG_LOCKREF
bc08b449 LT	28	aligned_u64 lock_count;
	29	#endif
	30	struct {
	31	spinlock_t lock;
360f5479	32	int count;
bc08b449 LT	33	};
bc08b449 LT	34	};
0f8f2aaa WL	35	};
0f8f2aaa WL	36
2f4f12e5	37	extern void lockref_get(struct lockref *);
360f5479	38	extern int lockref_put_return(struct lockref *);
2f4f12e5 LT	39	extern int lockref_get_not_zero(struct lockref *);
	40	extern int lockref_get_or_lock(struct lockref *);
	41	extern int lockref_put_or_lock(struct lockref *);
0f8f2aaa	42
e7d33bb5 LT	43	extern void lockref_mark_dead(struct lockref *);
	44	extern int lockref_get_not_dead(struct lockref *);
	45
e66cf161 SW	46	/* Must be called under spinlock for reliable results */
	47	static inline int __lockref_is_dead(const struct lockref *l)
	48	{
	49	return ((int)l->count < 0);
	50	}
	51
0f8f2aaa	52	#endif /* __LINUX_LOCKREF_H */