[linux-2.6-block.git] / arch / sparc / include / asm / rwsem.h

/*
 * rwsem.h: R/W semaphores implemented using CAS
 *
 * Written by David S. Miller (davem@redhat.com), 2001.
 * Derived from asm-i386/rwsem.h
 */
#ifndef _SPARC64_RWSEM_H
#define _SPARC64_RWSEM_H

#ifndef _LINUX_RWSEM_H
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
#endif

#ifdef __KERNEL__
struct rw_semaphore {
	signed long			count;
#define RWSEM_UNLOCKED_VALUE		0x00000000L
#define RWSEM_ACTIVE_BIAS		0x00000001L
#define RWSEM_ACTIVE_MASK		0xffffffffL
#define RWSEM_WAITING_BIAS		(-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
	spinlock_t			wait_lock;
	struct list_head		wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	struct lockdep_map		dep_map;
#endif
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC
# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
#else
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif

#define __RWSEM_INITIALIZER(name) \
{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
  LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }

#define DECLARE_RWSEM(name) \
	struct rw_semaphore name = __RWSEM_INITIALIZER(name)

extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);

extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
			 struct lock_class_key *key);

#define init_rwsem(sem)						\
do {								\
	static struct lock_class_key __key;			\
								\
	__init_rwsem((sem), #sem, &__key);			\
} while (0)

/*
 * lock for reading
 */
static inline void __down_read(struct rw_semaphore *sem)
{
	if (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L))
		rwsem_down_read_failed(sem);
}

static inline int __down_read_trylock(struct rw_semaphore *sem)
{
	long tmp;

	while ((tmp = sem->count) >= 0L) {
		if (tmp == cmpxchg(&sem->count, tmp,
				   tmp + RWSEM_ACTIVE_READ_BIAS)) {
			return 1;
		}
	}
	return 0;
}

/*
 * lock for writing
 */
static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
	long tmp;

	tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS,
				  (atomic64_t *)(&sem->count));
	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
		rwsem_down_write_failed(sem);
}

static inline void __down_write(struct rw_semaphore *sem)
{
	__down_write_nested(sem, 0);
}

static inline int __down_write_trylock(struct rw_semaphore *sem)
{
	long tmp;

	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
		      RWSEM_ACTIVE_WRITE_BIAS);
	return tmp == RWSEM_UNLOCKED_VALUE;
}

/*
 * unlock after reading
 */
static inline void __up_read(struct rw_semaphore *sem)
{
	long tmp;

	tmp = atomic64_dec_return((atomic64_t *)(&sem->count));
	if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L))
		rwsem_wake(sem);
}

/*
 * unlock after writing
 */
static inline void __up_write(struct rw_semaphore *sem)
{
	if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
					 (atomic64_t *)(&sem->count)) < 0L))
		rwsem_wake(sem);
}

/*
 * implement atomic add functionality
 */
static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
{
	atomic64_add(delta, (atomic64_t *)(&sem->count));
}

/*
 * downgrade write lock to read lock
 */
static inline void __downgrade_write(struct rw_semaphore *sem)
{
	long tmp;

	tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count));
	if (tmp < 0L)
		rwsem_downgrade_wake(sem);
}

/*
 * implement exchange and add functionality
 */
static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
{
	return atomic64_add_return(delta, (atomic64_t *)(&sem->count));
}

static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
	return (sem->count != 0);
}

#endif /* __KERNEL__ */

#endif /* _SPARC64_RWSEM_H */
Commit	Line	Data
a00736e9 SR	1	/*
	2	* rwsem.h: R/W semaphores implemented using CAS
	3	*
	4	* Written by David S. Miller (davem@redhat.com), 2001.
	5	* Derived from asm-i386/rwsem.h
	6	*/
	7	#ifndef _SPARC64_RWSEM_H
	8	#define _SPARC64_RWSEM_H
	9
	10	#ifndef _LINUX_RWSEM_H
	11	#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
	12	#endif
	13
	14	#ifdef __KERNEL__
a00736e9	15	struct rw_semaphore {
9b3bb86a DM	16	signed long count;
	17	#define RWSEM_UNLOCKED_VALUE 0x00000000L
	18	#define RWSEM_ACTIVE_BIAS 0x00000001L
	19	#define RWSEM_ACTIVE_MASK 0xffffffffL
	20	#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
	21	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
	22	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
	23	spinlock_t wait_lock;
	24	struct list_head wait_list;
a00736e9	25	#ifdef CONFIG_DEBUG_LOCK_ALLOC
9b3bb86a	26	struct lockdep_map dep_map;
a00736e9 SR	27	#endif
	28	};
	29
	30	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	31	# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
	32	#else
	33	# define __RWSEM_DEP_MAP_INIT(lockname)
	34	#endif
	35
	36	#define __RWSEM_INITIALIZER(name) \
8a2fe6c7 TG	37	{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
8a2fe6c7 TG	38	LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
a00736e9 SR	39
	40	#define DECLARE_RWSEM(name) \
	41	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
	42
9b3bb86a DM	43	extern struct rw_semaphore rwsem_down_read_failed(struct rw_semaphore sem);
	44	extern struct rw_semaphore rwsem_down_write_failed(struct rw_semaphore sem);
	45	extern struct rw_semaphore rwsem_wake(struct rw_semaphore sem);
	46	extern struct rw_semaphore rwsem_downgrade_wake(struct rw_semaphore sem);
	47
a00736e9 SR	48	extern void __init_rwsem(struct rw_semaphore sem, const char name,
	49	struct lock_class_key *key);
	50
	51	#define init_rwsem(sem) \
	52	do { \
	53	static struct lock_class_key __key; \
	54	\
	55	__init_rwsem((sem), #sem, &__key); \
	56	} while (0)
	57
9b3bb86a DM	58	/*
	59	* lock for reading
	60	*/
	61	static inline void __down_read(struct rw_semaphore *sem)
	62	{
	63	if (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L))
	64	rwsem_down_read_failed(sem);
	65	}
	66
	67	static inline int __down_read_trylock(struct rw_semaphore *sem)
	68	{
	69	long tmp;
	70
	71	while ((tmp = sem->count) >= 0L) {
	72	if (tmp == cmpxchg(&sem->count, tmp,
	73	tmp + RWSEM_ACTIVE_READ_BIAS)) {
	74	return 1;
	75	}
	76	}
	77	return 0;
	78	}
a00736e9	79
9b3bb86a DM	80	/*
	81	* lock for writing
	82	*/
a00736e9 SR	83	static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
a00736e9 SR	84	{
9b3bb86a DM	85	long tmp;
	86
	87	tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS,
	88	(atomic64_t *)(&sem->count));
	89	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
	90	rwsem_down_write_failed(sem);
a00736e9 SR	91	}
a00736e9 SR	92
9b3bb86a	93	static inline void __down_write(struct rw_semaphore *sem)
a00736e9	94	{
9b3bb86a DM	95	__down_write_nested(sem, 0);
	96	}
	97
	98	static inline int __down_write_trylock(struct rw_semaphore *sem)
	99	{
	100	long tmp;
	101
	102	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
	103	RWSEM_ACTIVE_WRITE_BIAS);
	104	return tmp == RWSEM_UNLOCKED_VALUE;
a00736e9 SR	105	}
a00736e9 SR	106
9b3bb86a DM	107	/*
	108	* unlock after reading
	109	*/
	110	static inline void __up_read(struct rw_semaphore *sem)
	111	{
	112	long tmp;
	113
	114	tmp = atomic64_dec_return((atomic64_t *)(&sem->count));
	115	if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L))
	116	rwsem_wake(sem);
	117	}
	118
	119	/*
	120	* unlock after writing
	121	*/
	122	static inline void __up_write(struct rw_semaphore *sem)
	123	{
	124	if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
	125	(atomic64_t *)(&sem->count)) < 0L))
	126	rwsem_wake(sem);
	127	}
	128
	129	/*
	130	* implement atomic add functionality
	131	*/
	132	static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
	133	{
	134	atomic64_add(delta, (atomic64_t *)(&sem->count));
	135	}
	136
	137	/*
	138	* downgrade write lock to read lock
	139	*/
	140	static inline void __downgrade_write(struct rw_semaphore *sem)
	141	{
	142	long tmp;
	143
	144	tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count));
	145	if (tmp < 0L)
	146	rwsem_downgrade_wake(sem);
	147	}
	148
	149	/*
	150	* implement exchange and add functionality
	151	*/
	152	static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
a00736e9	153	{
9b3bb86a	154	return atomic64_add_return(delta, (atomic64_t *)(&sem->count));
a00736e9 SR	155	}
	156
	157	static inline int rwsem_is_locked(struct rw_semaphore *sem)
	158	{
	159	return (sem->count != 0);
	160	}
	161
	162	#endif /* __KERNEL__ */
	163
	164	#endif /* _SPARC64_RWSEM_H */