[deliverable/linux.git] / include / asm-powerpc / rwsem.h

#ifndef _ASM_POWERPC_RWSEM_H
#define _ASM_POWERPC_RWSEM_H

#ifdef __KERNEL__

/*
 * include/asm-powerpc/rwsem.h: R/W semaphores for PPC using the stuff
 * in lib/rwsem.c.  Adapted largely from include/asm-i386/rwsem.h
 * by Paul Mackerras <paulus@samba.org>.
 */

#include <linux/list.h>
#include <linux/spinlock.h>
#include <asm/atomic.h>
#include <asm/system.h>

/*
 * the semaphore definition
 */
struct rw_semaphore {
	/* XXX this should be able to be an atomic_t  -- paulus */
	signed int		count;
#define RWSEM_UNLOCKED_VALUE		0x00000000
#define RWSEM_ACTIVE_BIAS		0x00000001
#define RWSEM_ACTIVE_MASK		0x0000ffff
#define RWSEM_WAITING_BIAS		(-0x00010000)
#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;
};

#define __RWSEM_INITIALIZER(name) \
	{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
	  LIST_HEAD_INIT((name).wait_list) }

#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);

static inline void init_rwsem(struct rw_semaphore *sem)
{
	sem->count = RWSEM_UNLOCKED_VALUE;
	spin_lock_init(&sem->wait_lock);
	INIT_LIST_HEAD(&sem->wait_list);
}

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

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

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

/*
 * lock for writing
 */
static inline void __down_write(struct rw_semaphore *sem)
{
	int tmp;

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

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

	tmp = atomic_dec_return((atomic_t *)(&sem->count));
	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
		rwsem_wake(sem);
}

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

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

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

	tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
	if (tmp < 0)
		rwsem_downgrade_wake(sem);
}

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

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

#endif	/* __KERNEL__ */
#endif	/* _ASM_POWERPC_RWSEM_H */
Commit	Line	Data
342e73b3 JL	1	#ifndef _ASM_POWERPC_RWSEM_H
	2	#define _ASM_POWERPC_RWSEM_H
	3
	4	#ifdef __KERNEL__
	5
1da177e4	6	/*
2ef9481e	7	* include/asm-powerpc/rwsem.h: R/W semaphores for PPC using the stuff
1da177e4 LT	8	* in lib/rwsem.c. Adapted largely from include/asm-i386/rwsem.h
1da177e4 LT	9	* by Paul Mackerras <paulus@samba.org>.
1da177e4 LT	10	*/
1da177e4 LT	11
1da177e4 LT	12	#include <linux/list.h>
	13	#include <linux/spinlock.h>
	14	#include <asm/atomic.h>
	15	#include <asm/system.h>
	16
	17	/*
	18	* the semaphore definition
	19	*/
	20	struct rw_semaphore {
	21	/* XXX this should be able to be an atomic_t -- paulus */
	22	signed int count;
	23	#define RWSEM_UNLOCKED_VALUE 0x00000000
	24	#define RWSEM_ACTIVE_BIAS 0x00000001
	25	#define RWSEM_ACTIVE_MASK 0x0000ffff
	26	#define RWSEM_WAITING_BIAS (-0x00010000)
	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;
1da177e4 LT	31	};
1da177e4 LT	32
1da177e4 LT	33	#define __RWSEM_INITIALIZER(name) \
1da177e4 LT	34	{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
61f4c3d6	35	LIST_HEAD_INIT((name).wait_list) }
1da177e4 LT	36
	37	#define DECLARE_RWSEM(name) \
	38	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
	39
	40	extern struct rw_semaphore rwsem_down_read_failed(struct rw_semaphore sem);
	41	extern struct rw_semaphore rwsem_down_write_failed(struct rw_semaphore sem);
	42	extern struct rw_semaphore rwsem_wake(struct rw_semaphore sem);
	43	extern struct rw_semaphore rwsem_downgrade_wake(struct rw_semaphore sem);
	44
	45	static inline void init_rwsem(struct rw_semaphore *sem)
	46	{
	47	sem->count = RWSEM_UNLOCKED_VALUE;
	48	spin_lock_init(&sem->wait_lock);
	49	INIT_LIST_HEAD(&sem->wait_list);
1da177e4 LT	50	}
	51
	52	/*
	53	* lock for reading
	54	*/
	55	static inline void __down_read(struct rw_semaphore *sem)
	56	{
	57	if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
	58	rwsem_down_read_failed(sem);
	59	}
	60
	61	static inline int __down_read_trylock(struct rw_semaphore *sem)
	62	{
	63	int tmp;
	64
	65	while ((tmp = sem->count) >= 0) {
	66	if (tmp == cmpxchg(&sem->count, tmp,
	67	tmp + RWSEM_ACTIVE_READ_BIAS)) {
	68	return 1;
	69	}
	70	}
	71	return 0;
	72	}
	73
	74	/*
	75	* lock for writing
	76	*/
	77	static inline void __down_write(struct rw_semaphore *sem)
	78	{
	79	int tmp;
	80
	81	tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
	82	(atomic_t *)(&sem->count));
	83	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
	84	rwsem_down_write_failed(sem);
	85	}
	86
	87	static inline int __down_write_trylock(struct rw_semaphore *sem)
	88	{
	89	int tmp;
	90
	91	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
	92	RWSEM_ACTIVE_WRITE_BIAS);
	93	return tmp == RWSEM_UNLOCKED_VALUE;
	94	}
	95
	96	/*
	97	* unlock after reading
	98	*/
	99	static inline void __up_read(struct rw_semaphore *sem)
	100	{
	101	int tmp;
	102
	103	tmp = atomic_dec_return((atomic_t *)(&sem->count));
	104	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
	105	rwsem_wake(sem);
	106	}
	107
	108	/*
	109	* unlock after writing
	110	*/
	111	static inline void __up_write(struct rw_semaphore *sem)
	112	{
	113	if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
114	(atomic_t *)(&sem->count)) < 0))
115	rwsem_wake(sem);
116	}
117
118	/*
119	* implement atomic add functionality
120	*/
121	static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
122	{
123	atomic_add(delta, (atomic_t *)(&sem->count));
124	}
125
126	/*
127	* downgrade write lock to read lock
128	*/
129	static inline void __downgrade_write(struct rw_semaphore *sem)
130	{
131	int tmp;
132
133	tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
134	if (tmp < 0)
135	rwsem_downgrade_wake(sem);
136	}
137
138	/*
139	* implement exchange and add functionality
140	*/
141	static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
142	{
143	return atomic_add_return(delta, (atomic_t *)(&sem->count));
144	}
145
eb92f4ef RVR	146	static inline int rwsem_is_locked(struct rw_semaphore *sem)
	147	{
	148	return (sem->count != 0);
	149	}
	150
342e73b3 JL	151	#endif /* __KERNEL__ */
342e73b3 JL	152	#endif /* _ASM_POWERPC_RWSEM_H */