[deliverable/linux.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 = atomic_long_read(&sem->count)) >= 0) {
		if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
				   tmp + RWSEM_ACTIVE_READ_BIAS)) {
			return 1;
		}
	}
	return 0;
}

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

	tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
				     (atomic_long_t *)&sem->count);
	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
		if (IS_ERR(rwsem_down_write_failed_killable(sem)))
			return -EINTR;
	return 0;
}

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

	tmp = atomic_long_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);
}

/*
 * 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);
}

#endif	/* __KERNEL__ */
#endif	/* _ASM_GENERIC_RWSEM_H */
Commit	Line	Data
	1	#ifndef _ASM_GENERIC_RWSEM_H
	2	#define _ASM_GENERIC_RWSEM_H
	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	/*
	11	* R/W semaphores originally for PPC using the stuff in lib/rwsem.c.
	12	* Adapted largely from include/asm-i386/rwsem.h
	13	* by Paul Mackerras <paulus@samba.org>.
	14	*/
	15
	16	/*
	17	* the semaphore definition
	18	*/
	19	#ifdef CONFIG_64BIT
	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	{
	36	if (unlikely(atomic_long_inc_return_acquire((atomic_long_t *)&sem->count) <= 0))
	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 = atomic_long_read(&sem->count)) >= 0) {
	45	if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
	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(struct rw_semaphore *sem)
	57	{
	58	long tmp;
	59
	60	tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
	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 int __down_write_killable(struct rw_semaphore *sem)
	67	{
	68	long tmp;
	69
	70	tmp = atomic_long_add_return_acquire(RWSEM_ACTIVE_WRITE_BIAS,
	71	(atomic_long_t *)&sem->count);
	72	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
	73	if (IS_ERR(rwsem_down_write_failed_killable(sem)))
	74	return -EINTR;
	75	return 0;
	76	}
	77
	78	static inline int __down_write_trylock(struct rw_semaphore *sem)
	79	{
	80	long tmp;
	81
	82	tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
	83	RWSEM_ACTIVE_WRITE_BIAS);
	84	return tmp == RWSEM_UNLOCKED_VALUE;
	85	}
	86
	87	/*
	88	* unlock after reading
	89	*/
	90	static inline void __up_read(struct rw_semaphore *sem)
	91	{
	92	long tmp;
	93
	94	tmp = atomic_long_dec_return_release((atomic_long_t *)&sem->count);
	95	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
	96	rwsem_wake(sem);
	97	}
	98
	99	/*
	100	* unlock after writing
	101	*/
	102	static inline void __up_write(struct rw_semaphore *sem)
	103	{
	104	if (unlikely(atomic_long_sub_return_release(RWSEM_ACTIVE_WRITE_BIAS,
	105	(atomic_long_t *)&sem->count) < 0))
	106	rwsem_wake(sem);
	107	}
	108
	109	/*
	110	* downgrade write lock to read lock
	111	*/
	112	static inline void __downgrade_write(struct rw_semaphore *sem)
	113	{
	114	long tmp;
	115
	116	/*
	117	* When downgrading from exclusive to shared ownership,
	118	* anything inside the write-locked region cannot leak
	119	* into the read side. In contrast, anything in the
	120	* read-locked region is ok to be re-ordered into the
	121	* write side. As such, rely on RELEASE semantics.
	122	*/
	123	tmp = atomic_long_add_return_release(-RWSEM_WAITING_BIAS,
	124	(atomic_long_t *)&sem->count);
	125	if (tmp < 0)
	126	rwsem_downgrade_wake(sem);
	127	}
	128
	129	#endif /* __KERNEL__ */
	130	#endif /* _ASM_GENERIC_RWSEM_H */