1 #ifndef _ASM_GENERIC_RWSEM_H
2 #define _ASM_GENERIC_RWSEM_H
5 #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
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>.
17 * the semaphore definition
20 # define RWSEM_ACTIVE_MASK 0xffffffffL
22 # define RWSEM_ACTIVE_MASK 0x0000ffffL
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)
34 static inline void __down_read(struct rw_semaphore *sem)
36 if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
37 rwsem_down_read_failed(sem);
40 static inline int __down_read_trylock(struct rw_semaphore *sem)
44 while ((tmp = sem->count) >= 0) {
45 if (tmp == cmpxchg(&sem->count, tmp,
46 tmp + RWSEM_ACTIVE_READ_BIAS)) {
56 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
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);
66 static inline void __down_write(struct rw_semaphore *sem)
68 __down_write_nested(sem, 0);
71 static inline int __down_write_trylock(struct rw_semaphore *sem)
75 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
76 RWSEM_ACTIVE_WRITE_BIAS);
77 return tmp == RWSEM_UNLOCKED_VALUE;
81 * unlock after reading
83 static inline void __up_read(struct rw_semaphore *sem)
87 tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
88 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
93 * unlock after writing
95 static inline void __up_write(struct rw_semaphore *sem)
97 if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
98 (atomic_long_t *)&sem->count) < 0))
103 * implement atomic add functionality
105 static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
107 atomic_long_add(delta, (atomic_long_t *)&sem->count);
111 * downgrade write lock to read lock
113 static inline void __downgrade_write(struct rw_semaphore *sem)
117 tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
118 (atomic_long_t *)&sem->count);
120 rwsem_downgrade_wake(sem);
124 * implement exchange and add functionality
126 static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
128 return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
131 #endif /* __KERNEL__ */
132 #endif /* _ASM_GENERIC_RWSEM_H */