[linux-2.6-block.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;
#if RWSEM_DEBUG
	int			debug;
#endif
};

/*
 * initialisation
 */
#if RWSEM_DEBUG
#define __RWSEM_DEBUG_INIT      , 0
#else
#define __RWSEM_DEBUG_INIT	/* */
#endif

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

#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);
#if RWSEM_DEBUG
	sem->debug = 0;
#endif
}

/*
 * 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;
	31	#if RWSEM_DEBUG
	32	int debug;
	33	#endif
	34	};
	35
	36	/*
	37	* initialisation
	38	*/
	39	#if RWSEM_DEBUG
	40	#define __RWSEM_DEBUG_INIT , 0
	41	#else
	42	#define __RWSEM_DEBUG_INIT /* */
	43	#endif
	44
	45	#define __RWSEM_INITIALIZER(name) \
	46	{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
	47	LIST_HEAD_INIT((name).wait_list) \
	48	__RWSEM_DEBUG_INIT }
	49
	50	#define DECLARE_RWSEM(name) \
	51	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
	52
	53	extern struct rw_semaphore rwsem_down_read_failed(struct rw_semaphore sem);
	54	extern struct rw_semaphore rwsem_down_write_failed(struct rw_semaphore sem);
	55	extern struct rw_semaphore rwsem_wake(struct rw_semaphore sem);
	56	extern struct rw_semaphore rwsem_downgrade_wake(struct rw_semaphore sem);
	57
	58	static inline void init_rwsem(struct rw_semaphore *sem)
	59	{
	60	sem->count = RWSEM_UNLOCKED_VALUE;
	61	spin_lock_init(&sem->wait_lock);
	62	INIT_LIST_HEAD(&sem->wait_list);
	63	#if RWSEM_DEBUG
	64	sem->debug = 0;
	65	#endif
	66	}
	67
	68	/*
	69	* lock for reading
	70	*/
	71	static inline void __down_read(struct rw_semaphore *sem)
	72	{
	73	if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
	74	rwsem_down_read_failed(sem);
	75	}
76
77	static inline int __down_read_trylock(struct rw_semaphore *sem)
78	{
79	int tmp;
80
81	while ((tmp = sem->count) >= 0) {
82	if (tmp == cmpxchg(&sem->count, tmp,
83	tmp + RWSEM_ACTIVE_READ_BIAS)) {
84	return 1;
85	}
86	}
87	return 0;
88	}
89
90	/*
91	* lock for writing
92	*/
93	static inline void __down_write(struct rw_semaphore *sem)
94	{
95	int tmp;
96
97	tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
98	(atomic_t *)(&sem->count));
99	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
100	rwsem_down_write_failed(sem);
101	}
102
103	static inline int __down_write_trylock(struct rw_semaphore *sem)
104	{
105	int tmp;
106
107	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
108	RWSEM_ACTIVE_WRITE_BIAS);
109	return tmp == RWSEM_UNLOCKED_VALUE;
110	}
111
112	/*
113	* unlock after reading
114	*/
115	static inline void __up_read(struct rw_semaphore *sem)
116	{
117	int tmp;
118
119	tmp = atomic_dec_return((atomic_t *)(&sem->count));
120	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
121	rwsem_wake(sem);
122	}
123
124	/*
125	* unlock after writing
126	*/
127	static inline void __up_write(struct rw_semaphore *sem)
128	{
129	if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
130	(atomic_t *)(&sem->count)) < 0))
131	rwsem_wake(sem);
132	}
133
134	/*
135	* implement atomic add functionality
136	*/
137	static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
138	{
139	atomic_add(delta, (atomic_t *)(&sem->count));
140	}
141
142	/*
143	* downgrade write lock to read lock
144	*/
145	static inline void __downgrade_write(struct rw_semaphore *sem)
146	{
147	int tmp;
148
149	tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
150	if (tmp < 0)
151	rwsem_downgrade_wake(sem);
152	}
153
154	/*
155	* implement exchange and add functionality
156	*/
157	static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
158	{
159	return atomic_add_return(delta, (atomic_t *)(&sem->count));
160	}
161
eb92f4ef RVR	162	static inline int rwsem_is_locked(struct rw_semaphore *sem)
	163	{
	164	return (sem->count != 0);
	165	}
	166
342e73b3 JL	167	#endif /* __KERNEL__ */
342e73b3 JL	168	#endif /* _ASM_POWERPC_RWSEM_H */