1 #ifndef _ASM_POWERPC_RWSEM_H
2 #define _ASM_POWERPC_RWSEM_H
5 #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
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>.
16 #include <linux/list.h>
17 #include <linux/spinlock.h>
18 #include <asm/atomic.h>
19 #include <asm/system.h>
22 * the semaphore definition
25 # define RWSEM_ACTIVE_MASK 0xffffffffL
27 # define RWSEM_ACTIVE_MASK 0x0000ffffL
30 #define RWSEM_UNLOCKED_VALUE 0x00000000L
31 #define RWSEM_ACTIVE_BIAS 0x00000001L
32 #define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
33 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
34 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
39 struct list_head wait_list;
40 #ifdef CONFIG_DEBUG_LOCK_ALLOC
41 struct lockdep_map dep_map;
45 #ifdef CONFIG_DEBUG_LOCK_ALLOC
46 # define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
48 # define __RWSEM_DEP_MAP_INIT(lockname)
51 #define __RWSEM_INITIALIZER(name) \
53 RWSEM_UNLOCKED_VALUE, \
54 __SPIN_LOCK_UNLOCKED((name).wait_lock), \
55 LIST_HEAD_INIT((name).wait_list) \
56 __RWSEM_DEP_MAP_INIT(name) \
59 #define DECLARE_RWSEM(name) \
60 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
62 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
63 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
64 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
65 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
67 extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
68 struct lock_class_key *key);
70 #define init_rwsem(sem) \
72 static struct lock_class_key __key; \
74 __init_rwsem((sem), #sem, &__key); \
80 static inline void __down_read(struct rw_semaphore *sem)
82 if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
83 rwsem_down_read_failed(sem);
86 static inline int __down_read_trylock(struct rw_semaphore *sem)
90 while ((tmp = sem->count) >= 0) {
91 if (tmp == cmpxchg(&sem->count, tmp,
92 tmp + RWSEM_ACTIVE_READ_BIAS)) {
102 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
106 tmp = atomic_long_add_return(RWSEM_ACTIVE_WRITE_BIAS,
107 (atomic_long_t *)&sem->count);
108 if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
109 rwsem_down_write_failed(sem);
112 static inline void __down_write(struct rw_semaphore *sem)
114 __down_write_nested(sem, 0);
117 static inline int __down_write_trylock(struct rw_semaphore *sem)
121 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
122 RWSEM_ACTIVE_WRITE_BIAS);
123 return tmp == RWSEM_UNLOCKED_VALUE;
127 * unlock after reading
129 static inline void __up_read(struct rw_semaphore *sem)
133 tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
134 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
139 * unlock after writing
141 static inline void __up_write(struct rw_semaphore *sem)
143 if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
144 (atomic_long_t *)&sem->count) < 0))
149 * implement atomic add functionality
151 static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
153 atomic_long_add(delta, (atomic_long_t *)&sem->count);
157 * downgrade write lock to read lock
159 static inline void __downgrade_write(struct rw_semaphore *sem)
163 tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
164 (atomic_long_t *)&sem->count);
166 rwsem_downgrade_wake(sem);
170 * implement exchange and add functionality
172 static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
174 return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
177 static inline int rwsem_is_locked(struct rw_semaphore *sem)
179 return sem->count != 0;
182 #endif /* __KERNEL__ */
183 #endif /* _ASM_POWERPC_RWSEM_H */