[deliverable/linux.git] / arch / sh / include / asm / rwsem.h

/*
 * include/asm-sh/rwsem.h: R/W semaphores for SH using the stuff
 * in lib/rwsem.c.
 */

#ifndef _ASM_SH_RWSEM_H
#define _ASM_SH_RWSEM_H

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

#ifdef __KERNEL__

#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)

/*
 * lock for reading
 */
static inline void __down_read(struct rw_semaphore *sem)
{
	if (atomic_inc_return((atomic_t *)(&sem->count)) > 0)
		smp_wmb();
	else
		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)) {
			smp_wmb();
			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 (tmp == RWSEM_ACTIVE_WRITE_BIAS)
		smp_wmb();
	else
		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);
	smp_wmb();
	return tmp == RWSEM_UNLOCKED_VALUE;
}

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

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

/*
 * unlock after writing
 */
static inline void __up_write(struct rw_semaphore *sem)
{
	smp_wmb();
	if (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;

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

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

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

#endif /* __KERNEL__ */
#endif /* _ASM_SH_RWSEM_H */
Commit	Line	Data
1da177e4	1	/*
711be605	2	* include/asm-sh/rwsem.h: R/W semaphores for SH using the stuff
1da177e4 LT	3	* in lib/rwsem.c.
	4	*/
	5
	6	#ifndef _ASM_SH_RWSEM_H
	7	#define _ASM_SH_RWSEM_H
	8
711be605 RD	9	#ifndef _LINUX_RWSEM_H
	10	#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
	11	#endif
	12
1da177e4	13	#ifdef __KERNEL__
1c8ed640	14
1da177e4 LT	15	#define RWSEM_UNLOCKED_VALUE 0x00000000
	16	#define RWSEM_ACTIVE_BIAS 0x00000001
	17	#define RWSEM_ACTIVE_MASK 0x0000ffff
	18	#define RWSEM_WAITING_BIAS (-0x00010000)
	19	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
	20	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
1da177e4	21
1da177e4 LT	22	/*
	23	* lock for reading
	24	*/
	25	static inline void __down_read(struct rw_semaphore *sem)
	26	{
	27	if (atomic_inc_return((atomic_t *)(&sem->count)) > 0)
	28	smp_wmb();
	29	else
	30	rwsem_down_read_failed(sem);
	31	}
	32
	33	static inline int __down_read_trylock(struct rw_semaphore *sem)
	34	{
	35	int tmp;
	36
	37	while ((tmp = sem->count) >= 0) {
	38	if (tmp == cmpxchg(&sem->count, tmp,
	39	tmp + RWSEM_ACTIVE_READ_BIAS)) {
	40	smp_wmb();
	41	return 1;
	42	}
	43	}
	44	return 0;
	45	}
	46
	47	/*
	48	* lock for writing
	49	*/
	50	static inline void __down_write(struct rw_semaphore *sem)
	51	{
	52	int tmp;
	53
	54	tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
	55	(atomic_t *)(&sem->count));
	56	if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
	57	smp_wmb();
	58	else
	59	rwsem_down_write_failed(sem);
	60	}
	61
	62	static inline int __down_write_trylock(struct rw_semaphore *sem)
	63	{
	64	int tmp;
	65
	66	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
	67	RWSEM_ACTIVE_WRITE_BIAS);
	68	smp_wmb();
	69	return tmp == RWSEM_UNLOCKED_VALUE;
	70	}
	71
	72	/*
	73	* unlock after reading
	74	*/
	75	static inline void __up_read(struct rw_semaphore *sem)
	76	{
	77	int tmp;
	78
	79	smp_wmb();
	80	tmp = atomic_dec_return((atomic_t *)(&sem->count));
	81	if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
	82	rwsem_wake(sem);
	83	}
	84
	85	/*
86	* unlock after writing
87	*/
88	static inline void __up_write(struct rw_semaphore *sem)
89	{
90	smp_wmb();
91	if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
92	(atomic_t *)(&sem->count)) < 0)
93	rwsem_wake(sem);
94	}
95
96	/*
97	* implement atomic add functionality
98	*/
99	static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
100	{
101	atomic_add(delta, (atomic_t *)(&sem->count));
102	}
103
104	/*
105	* downgrade write lock to read lock
106	*/
107	static inline void __downgrade_write(struct rw_semaphore *sem)
108	{
109	int tmp;
110
111	smp_wmb();
112	tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
113	if (tmp < 0)
114	rwsem_downgrade_wake(sem);
115	}
116
afbfb52e PM	117	static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
	118	{
	119	__down_write(sem);
	120	}
	121
1da177e4 LT	122	/*
	123	* implement exchange and add functionality
	124	*/
	125	static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
	126	{
	127	smp_mb();
	128	return atomic_add_return(delta, (atomic_t *)(&sem->count));
	129	}
	130
	131	#endif /* __KERNEL__ */
	132	#endif /* _ASM_SH_RWSEM_H */