[net-next-2.6.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__

#include <linux/list.h>
#include <linux/spinlock.h>

struct rwsem_waiter;

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__
	15
	16	#include <linux/list.h>
	17	#include <linux/spinlock.h>
a00736e9 SR	18
	19	struct rwsem_waiter;
	20
	21	struct rw_semaphore {
9b3bb86a DM	22	signed long count;
	23	#define RWSEM_UNLOCKED_VALUE 0x00000000L
	24	#define RWSEM_ACTIVE_BIAS 0x00000001L
	25	#define RWSEM_ACTIVE_MASK 0xffffffffL
	26	#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
	27	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
	28	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
	29	spinlock_t wait_lock;
	30	struct list_head wait_list;
a00736e9	31	#ifdef CONFIG_DEBUG_LOCK_ALLOC
9b3bb86a	32	struct lockdep_map dep_map;
a00736e9 SR	33	#endif
	34	};
	35
	36	#ifdef CONFIG_DEBUG_LOCK_ALLOC
	37	# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
	38	#else
	39	# define __RWSEM_DEP_MAP_INIT(lockname)
	40	#endif
	41
	42	#define __RWSEM_INITIALIZER(name) \
8a2fe6c7 TG	43	{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
8a2fe6c7 TG	44	LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
a00736e9 SR	45
	46	#define DECLARE_RWSEM(name) \
	47	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
	48
9b3bb86a DM	49	extern struct rw_semaphore rwsem_down_read_failed(struct rw_semaphore sem);
	50	extern struct rw_semaphore rwsem_down_write_failed(struct rw_semaphore sem);
	51	extern struct rw_semaphore rwsem_wake(struct rw_semaphore sem);
	52	extern struct rw_semaphore rwsem_downgrade_wake(struct rw_semaphore sem);
	53
a00736e9 SR	54	extern void __init_rwsem(struct rw_semaphore sem, const char name,
	55	struct lock_class_key *key);
	56
	57	#define init_rwsem(sem) \
	58	do { \
	59	static struct lock_class_key __key; \
	60	\
	61	__init_rwsem((sem), #sem, &__key); \
	62	} while (0)
	63
9b3bb86a DM	64	/*
	65	* lock for reading
	66	*/
	67	static inline void __down_read(struct rw_semaphore *sem)
	68	{
	69	if (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L))
	70	rwsem_down_read_failed(sem);
	71	}
	72
	73	static inline int __down_read_trylock(struct rw_semaphore *sem)
	74	{
	75	long tmp;
	76
	77	while ((tmp = sem->count) >= 0L) {
	78	if (tmp == cmpxchg(&sem->count, tmp,
	79	tmp + RWSEM_ACTIVE_READ_BIAS)) {
	80	return 1;
	81	}
	82	}
	83	return 0;
	84	}
a00736e9	85
9b3bb86a DM	86	/*
	87	* lock for writing
	88	*/
a00736e9 SR	89	static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
a00736e9 SR	90	{
9b3bb86a DM	91	long tmp;
	92
	93	tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS,
	94	(atomic64_t *)(&sem->count));
	95	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
	96	rwsem_down_write_failed(sem);
a00736e9 SR	97	}
a00736e9 SR	98
9b3bb86a	99	static inline void __down_write(struct rw_semaphore *sem)
a00736e9	100	{
9b3bb86a DM	101	__down_write_nested(sem, 0);
	102	}
	103
	104	static inline int __down_write_trylock(struct rw_semaphore *sem)
	105	{
	106	long tmp;
	107
	108	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
	109	RWSEM_ACTIVE_WRITE_BIAS);
	110	return tmp == RWSEM_UNLOCKED_VALUE;
a00736e9 SR	111	}
a00736e9 SR	112
9b3bb86a DM	113	/*
	114	* unlock after reading
	115	*/
	116	static inline void __up_read(struct rw_semaphore *sem)
	117	{
	118	long tmp;
	119
	120	tmp = atomic64_dec_return((atomic64_t *)(&sem->count));
	121	if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L))
	122	rwsem_wake(sem);
	123	}
	124
	125	/*
	126	* unlock after writing
	127	*/
	128	static inline void __up_write(struct rw_semaphore *sem)
	129	{
	130	if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
	131	(atomic64_t *)(&sem->count)) < 0L))
	132	rwsem_wake(sem);
	133	}
	134
	135	/*
	136	* implement atomic add functionality
	137	*/
	138	static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
	139	{
	140	atomic64_add(delta, (atomic64_t *)(&sem->count));
	141	}
	142
	143	/*
	144	* downgrade write lock to read lock
	145	*/
	146	static inline void __downgrade_write(struct rw_semaphore *sem)
	147	{
	148	long tmp;
	149
	150	tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count));
	151	if (tmp < 0L)
	152	rwsem_downgrade_wake(sem);
	153	}
	154
	155	/*
	156	* implement exchange and add functionality
	157	*/
	158	static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
a00736e9	159	{
9b3bb86a	160	return atomic64_add_return(delta, (atomic64_t *)(&sem->count));
a00736e9 SR	161	}
	162
	163	static inline int rwsem_is_locked(struct rw_semaphore *sem)
	164	{
	165	return (sem->count != 0);
	166	}
	167
	168	#endif /* __KERNEL__ */
	169
	170	#endif /* _SPARC64_RWSEM_H */