Linux 2.6.26-rc5
[linux-2.6/openmoko-kernel/knife-kernel.git] / include / asm-powerpc / rwsem.h
bloba6cc93b78b981eaff6fb3f4944afcb686563e572
1 #ifndef _ASM_POWERPC_RWSEM_H
2 #define _ASM_POWERPC_RWSEM_H
4 #ifndef _LINUX_RWSEM_H
5 #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
6 #endif
8 #ifdef __KERNEL__
11 * include/asm-powerpc/rwsem.h: R/W semaphores for PPC using the stuff
12 * in lib/rwsem.c. 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
24 struct 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
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
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) }
50 #define DECLARE_RWSEM(name) \
51 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
53 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
54 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
55 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
56 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
58 extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
59 struct lock_class_key *key);
61 #define init_rwsem(sem) \
62 do { \
63 static struct lock_class_key __key; \
65 __init_rwsem((sem), #sem, &__key); \
66 } while (0)
69 * lock for reading
71 static inline void __down_read(struct rw_semaphore *sem)
73 if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
74 rwsem_down_read_failed(sem);
77 static inline int __down_read_trylock(struct rw_semaphore *sem)
79 int tmp;
81 while ((tmp = sem->count) >= 0) {
82 if (tmp == cmpxchg(&sem->count, tmp,
83 tmp + RWSEM_ACTIVE_READ_BIAS)) {
84 return 1;
87 return 0;
91 * lock for writing
93 static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
95 int tmp;
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);
103 static inline void __down_write(struct rw_semaphore *sem)
105 __down_write_nested(sem, 0);
108 static inline int __down_write_trylock(struct rw_semaphore *sem)
110 int tmp;
112 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
113 RWSEM_ACTIVE_WRITE_BIAS);
114 return tmp == RWSEM_UNLOCKED_VALUE;
118 * unlock after reading
120 static inline void __up_read(struct rw_semaphore *sem)
122 int tmp;
124 tmp = atomic_dec_return((atomic_t *)(&sem->count));
125 if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
126 rwsem_wake(sem);
130 * unlock after writing
132 static inline void __up_write(struct rw_semaphore *sem)
134 if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
135 (atomic_t *)(&sem->count)) < 0))
136 rwsem_wake(sem);
140 * implement atomic add functionality
142 static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
144 atomic_add(delta, (atomic_t *)(&sem->count));
148 * downgrade write lock to read lock
150 static inline void __downgrade_write(struct rw_semaphore *sem)
152 int tmp;
154 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
155 if (tmp < 0)
156 rwsem_downgrade_wake(sem);
160 * implement exchange and add functionality
162 static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
164 return atomic_add_return(delta, (atomic_t *)(&sem->count));
167 static inline int rwsem_is_locked(struct rw_semaphore *sem)
169 return (sem->count != 0);
172 #endif /* __KERNEL__ */
173 #endif /* _ASM_POWERPC_RWSEM_H */