fs: use kmem_cache_zalloc instead
[pv_ops_mirror.git] / include / asm-xtensa / rwsem.h
blob0aad3a5875516a3c640b5e7cddf41cf7c044225f
1 /*
2 * include/asm-xtensa/rwsem.h
4 * This file is subject to the terms and conditions of the GNU General Public
5 * License. See the file "COPYING" in the main directory of this archive
6 * for more details.
8 * Largely copied from include/asm-ppc/rwsem.h
10 * Copyright (C) 2001 - 2005 Tensilica Inc.
13 #ifndef _XTENSA_RWSEM_H
14 #define _XTENSA_RWSEM_H
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 signed long count;
26 #define RWSEM_UNLOCKED_VALUE 0x00000000
27 #define RWSEM_ACTIVE_BIAS 0x00000001
28 #define RWSEM_ACTIVE_MASK 0x0000ffff
29 #define RWSEM_WAITING_BIAS (-0x00010000)
30 #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
31 #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
32 spinlock_t wait_lock;
33 struct list_head wait_list;
36 #define __RWSEM_INITIALIZER(name) \
37 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
38 LIST_HEAD_INIT((name).wait_list) }
40 #define DECLARE_RWSEM(name) \
41 struct rw_semaphore name = __RWSEM_INITIALIZER(name)
43 extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
44 extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
45 extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
46 extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
48 static inline void init_rwsem(struct rw_semaphore *sem)
50 sem->count = RWSEM_UNLOCKED_VALUE;
51 spin_lock_init(&sem->wait_lock);
52 INIT_LIST_HEAD(&sem->wait_list);
56 * lock for reading
58 static inline void __down_read(struct rw_semaphore *sem)
60 if (atomic_add_return(1,(atomic_t *)(&sem->count)) > 0)
61 smp_wmb();
62 else
63 rwsem_down_read_failed(sem);
66 static inline int __down_read_trylock(struct rw_semaphore *sem)
68 int tmp;
70 while ((tmp = sem->count) >= 0) {
71 if (tmp == cmpxchg(&sem->count, tmp,
72 tmp + RWSEM_ACTIVE_READ_BIAS)) {
73 smp_wmb();
74 return 1;
77 return 0;
81 * lock for writing
83 static inline void __down_write(struct rw_semaphore *sem)
85 int tmp;
87 tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
88 (atomic_t *)(&sem->count));
89 if (tmp == RWSEM_ACTIVE_WRITE_BIAS)
90 smp_wmb();
91 else
92 rwsem_down_write_failed(sem);
95 static inline int __down_write_trylock(struct rw_semaphore *sem)
97 int tmp;
99 tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
100 RWSEM_ACTIVE_WRITE_BIAS);
101 smp_wmb();
102 return tmp == RWSEM_UNLOCKED_VALUE;
106 * unlock after reading
108 static inline void __up_read(struct rw_semaphore *sem)
110 int tmp;
112 smp_wmb();
113 tmp = atomic_sub_return(1,(atomic_t *)(&sem->count));
114 if (tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0)
115 rwsem_wake(sem);
119 * unlock after writing
121 static inline void __up_write(struct rw_semaphore *sem)
123 smp_wmb();
124 if (atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
125 (atomic_t *)(&sem->count)) < 0)
126 rwsem_wake(sem);
130 * implement atomic add functionality
132 static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
134 atomic_add(delta, (atomic_t *)(&sem->count));
138 * downgrade write lock to read lock
140 static inline void __downgrade_write(struct rw_semaphore *sem)
142 int tmp;
144 smp_wmb();
145 tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
146 if (tmp < 0)
147 rwsem_downgrade_wake(sem);
151 * implement exchange and add functionality
153 static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
155 smp_mb();
156 return atomic_add_return(delta, (atomic_t *)(&sem->count));
159 static inline int rwsem_is_locked(struct rw_semaphore *sem)
161 return (sem->count != 0);
164 #endif /* _XTENSA_RWSEM_H */