1#ifndef _ASM_POWERPC_RWSEM_H
  2#define _ASM_POWERPC_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 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_PPC64
 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 */
 34static inline void __down_read(struct rw_semaphore *sem)
 35{
 36	if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
 37		rwsem_down_read_failed(sem);
 38}
 39
 40static inline int __down_read_trylock(struct rw_semaphore *sem)
 41{
 42	long tmp;
 43
 44	while ((tmp = sem->count) >= 0) {
 45		if (tmp == cmpxchg(&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 */
 56static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 57{
 58	long tmp;
 59
 60	tmp = atomic_long_add_return(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
 66static inline void __down_write(struct rw_semaphore *sem)
 67{
 68	__down_write_nested(sem, 0);
 69}
 70
 71static inline int __down_write_trylock(struct rw_semaphore *sem)
 72{
 73	long tmp;
 74
 75	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
 76		      RWSEM_ACTIVE_WRITE_BIAS);
 77	return tmp == RWSEM_UNLOCKED_VALUE;
 78}
 79
 80/*
 81 * unlock after reading
 82 */
 83static inline void __up_read(struct rw_semaphore *sem)
 84{
 85	long tmp;
 86
 87	tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
 88	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
 89		rwsem_wake(sem);
 90}
 91
 92/*
 93 * unlock after writing
 94 */
 95static inline void __up_write(struct rw_semaphore *sem)
 96{
 97	if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
 98				 (atomic_long_t *)&sem->count) < 0))
 99		rwsem_wake(sem);
100}
101
102/*
103 * implement atomic add functionality
104 */
105static 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 */
113static inline void __downgrade_write(struct rw_semaphore *sem)
114{
115	long tmp;
116
117	tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
118				     (atomic_long_t *)&sem->count);
119	if (tmp < 0)
120		rwsem_downgrade_wake(sem);
121}
122
123/*
124 * implement exchange and add functionality
125 */
126static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
127{
128	return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
129}
130
131#endif	/* __KERNEL__ */
132#endif	/* _ASM_POWERPC_RWSEM_H */