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

#ifndef _ASM_GENERIC_RWSEM_H
#define _ASM_GENERIC_RWSEM_H

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

#ifdef __KERNEL__

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

/*
 * the semaphore definition
 */
#ifdef CONFIG_64BIT
# define RWSEM_ACTIVE_MASK		0xffffffffL
#else
# define RWSEM_ACTIVE_MASK		0x0000ffffL
#endif

#define RWSEM_UNLOCKED_VALUE		0x00000000L
#define RWSEM_ACTIVE_BIAS		0x00000001L
#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)

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

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

	while ((tmp = sem->count) >= 0) {
		if (tmp == cmpxchg_acquire(&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 = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
				     (atomic_long_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_acquire(&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 = atomic_long_dec_return_release((atomic_long_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_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
				 (atomic_long_t *)&sem->count) < 0))
		rwsem_wake(sem);
}

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

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

	/*
	 * When downgrading from exclusive to shared ownership,
	 * anything inside the write-locked region cannot leak
	 * into the read side. In contrast, anything in the
	 * read-locked region is ok to be re-ordered into the
	 * write side. As such, rely on RELEASE semantics.
	 */
	tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS,
				     (atomic_long_t *)&sem->count);
	if (tmp < 0)
		rwsem_downgrade_wake(sem);
}

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

#endif	/* __KERNEL__ */
#endif	/* _ASM_GENERIC_RWSEM_H */
Commit	Line	Data
e172800e WD	1	#ifndef _ASM_GENERIC_RWSEM_H
e172800e WD	2	#define _ASM_GENERIC_RWSEM_H
dd472da3 RK	3
	4	#ifndef _LINUX_RWSEM_H
	5	#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
	6	#endif
	7
	8	#ifdef __KERNEL__
	9
	10	/*
e172800e	11	* R/W semaphores originally for PPC using the stuff in lib/rwsem.c.
dd472da3 RK	12	* Adapted largely from include/asm-i386/rwsem.h
	13	* by Paul Mackerras <paulus@samba.org>.
	14	*/
	15
	16	/*
	17	* the semaphore definition
	18	*/
e172800e	19	#ifdef CONFIG_64BIT
dd472da3 RK	20	# define RWSEM_ACTIVE_MASK 0xffffffffL
	21	#else
	22	# define RWSEM_ACTIVE_MASK 0x0000ffffL
	23	#endif
	24
	25	#define RWSEM_UNLOCKED_VALUE 0x00000000L
	26	#define RWSEM_ACTIVE_BIAS 0x00000001L
	27	#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
	28	#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
	29	#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
	30
	31	/*
	32	* lock for reading
	33	*/
	34	static inline void __down_read(struct rw_semaphore *sem)
	35	{
00eb4bab	36	if (unlikely(atomic_long_inc_return_acquire((atomic_long_t *)&sem->count) <= 0))
dd472da3 RK	37	rwsem_down_read_failed(sem);
	38	}
	39
	40	static inline int __down_read_trylock(struct rw_semaphore *sem)
	41	{
	42	long tmp;
	43
	44	while ((tmp = sem->count) >= 0) {
00eb4bab	45	if (tmp == cmpxchg_acquire(&sem->count, tmp,
dd472da3 RK	46	tmp + RWSEM_ACTIVE_READ_BIAS)) {
	47	return 1;
	48	}
	49	}
	50	return 0;
	51	}
	52
	53	/*
	54	* lock for writing
	55	*/
	56	static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
	57	{
	58	long tmp;
	59
00eb4bab	60	tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
dd472da3 RK	61	(atomic_long_t *)&sem->count);
	62	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
	63	rwsem_down_write_failed(sem);
	64	}
	65
	66	static inline void __down_write(struct rw_semaphore *sem)
	67	{
	68	__down_write_nested(sem, 0);
	69	}
	70
	71	static inline int __down_write_trylock(struct rw_semaphore *sem)
	72	{
	73	long tmp;
	74
00eb4bab	75	tmp = cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
dd472da3 RK	76	RWSEM_ACTIVE_WRITE_BIAS);
	77	return tmp == RWSEM_UNLOCKED_VALUE;
	78	}
	79
	80	/*
	81	* unlock after reading
	82	*/
	83	static inline void __up_read(struct rw_semaphore *sem)
	84	{
	85	long tmp;
	86
00eb4bab	87	tmp = atomic_long_dec_return_release((atomic_long_t *)&sem->count);
dd472da3 RK	88	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
	89	rwsem_wake(sem);
	90	}
	91
	92	/*
	93	* unlock after writing
	94	*/
	95	static inline void __up_write(struct rw_semaphore *sem)
	96	{
00eb4bab	97	if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
dd472da3 RK	98	(atomic_long_t *)&sem->count) < 0))
	99	rwsem_wake(sem);
	100	}
	101
	102	/*
	103	* implement atomic add functionality
	104	*/
	105	static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
	106	{
	107	atomic_long_add(delta, (atomic_long_t *)&sem->count);
	108	}
	109
	110	/*
	111	* downgrade write lock to read lock
	112	*/
	113	static inline void __downgrade_write(struct rw_semaphore *sem)
	114	{
	115	long tmp;
	116
00eb4bab DB	117	/*
	118	* When downgrading from exclusive to shared ownership,
	119	* anything inside the write-locked region cannot leak
	120	* into the read side. In contrast, anything in the
	121	* read-locked region is ok to be re-ordered into the
	122	* write side. As such, rely on RELEASE semantics.
	123	*/
	124	tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS,
dd472da3 RK	125	(atomic_long_t *)&sem->count);
	126	if (tmp < 0)
	127	rwsem_downgrade_wake(sem);
	128	}
	129
	130	/*
	131	* implement exchange and add functionality
	132	*/
	133	static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
	134	{
	135	return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
	136	}
	137
	138	#endif /* __KERNEL__ */
e172800e	139	#endif /* _ASM_GENERIC_RWSEM_H */