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/arch/powerpc/include/asm/rwsem.h

https://bitbucket.org/cresqo/cm7-p500-kernel
C Header | 173 lines | 115 code | 28 blank | 30 comment | 14 complexity | 689f9239a237b1e099dae82bfe15a941 MD5 | raw file
Possible License(s): LGPL-2.0, AGPL-1.0, GPL-2.0
  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#include <linux/list.h>
 17#include <linux/spinlock.h>
 18#include <asm/atomic.h>
 19#include <asm/system.h>
 20
 21/*
 22 * the semaphore definition
 23 */
 24struct rw_semaphore {
 25	/* XXX this should be able to be an atomic_t  -- paulus */
 26	signed int		count;
 27#define RWSEM_UNLOCKED_VALUE		0x00000000
 28#define RWSEM_ACTIVE_BIAS		0x00000001
 29#define RWSEM_ACTIVE_MASK		0x0000ffff
 30#define RWSEM_WAITING_BIAS		(-0x00010000)
 31#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
 32#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
 33	spinlock_t		wait_lock;
 34	struct list_head	wait_list;
 35#ifdef CONFIG_DEBUG_LOCK_ALLOC
 36	struct lockdep_map	dep_map;
 37#endif
 38};
 39
 40#ifdef CONFIG_DEBUG_LOCK_ALLOC
 41# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
 42#else
 43# define __RWSEM_DEP_MAP_INIT(lockname)
 44#endif
 45
 46#define __RWSEM_INITIALIZER(name) \
 47	{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \
 48	  LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
 49
 50#define DECLARE_RWSEM(name)		\
 51	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
 52
 53extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
 54extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
 55extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
 56extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
 57
 58extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
 59			 struct lock_class_key *key);
 60
 61#define init_rwsem(sem)					\
 62	do {						\
 63		static struct lock_class_key __key;	\
 64							\
 65		__init_rwsem((sem), #sem, &__key);	\
 66	} while (0)
 67
 68/*
 69 * lock for reading
 70 */
 71static 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
 77static 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 */
 93static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 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
103static inline void __down_write(struct rw_semaphore *sem)
104{
105	__down_write_nested(sem, 0);
106}
107
108static inline int __down_write_trylock(struct rw_semaphore *sem)
109{
110	int tmp;
111
112	tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
113		      RWSEM_ACTIVE_WRITE_BIAS);
114	return tmp == RWSEM_UNLOCKED_VALUE;
115}
116
117/*
118 * unlock after reading
119 */
120static inline void __up_read(struct rw_semaphore *sem)
121{
122	int tmp;
123
124	tmp = atomic_dec_return((atomic_t *)(&sem->count));
125	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
126		rwsem_wake(sem);
127}
128
129/*
130 * unlock after writing
131 */
132static inline void __up_write(struct rw_semaphore *sem)
133{
134	if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
135			      (atomic_t *)(&sem->count)) < 0))
136		rwsem_wake(sem);
137}
138
139/*
140 * implement atomic add functionality
141 */
142static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
143{
144	atomic_add(delta, (atomic_t *)(&sem->count));
145}
146
147/*
148 * downgrade write lock to read lock
149 */
150static inline void __downgrade_write(struct rw_semaphore *sem)
151{
152	int tmp;
153
154	tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
155	if (tmp < 0)
156		rwsem_downgrade_wake(sem);
157}
158
159/*
160 * implement exchange and add functionality
161 */
162static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
163{
164	return atomic_add_return(delta, (atomic_t *)(&sem->count));
165}
166
167static inline int rwsem_is_locked(struct rw_semaphore *sem)
168{
169	return (sem->count != 0);
170}
171
172#endif	/* __KERNEL__ */
173#endif	/* _ASM_POWERPC_RWSEM_H */