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1da177e4 LT |
1 | /* |
2 | * asm-ia64/rwsem.h: R/W semaphores for ia64 | |
3 | * | |
4 | * Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com> | |
5 | * Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com> | |
16592d26 | 6 | * Copyright (C) 2005 Christoph Lameter <clameter@sgi.com> |
1da177e4 LT |
7 | * |
8 | * Based on asm-i386/rwsem.h and other architecture implementation. | |
9 | * | |
10 | * The MSW of the count is the negated number of active writers and | |
11 | * waiting lockers, and the LSW is the total number of active locks. | |
12 | * | |
13 | * The lock count is initialized to 0 (no active and no waiting lockers). | |
14 | * | |
16592d26 CL |
15 | * When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for |
16 | * the case of an uncontended lock. Readers increment by 1 and see a positive | |
17 | * value when uncontended, negative if there are writers (and maybe) readers | |
1da177e4 LT |
18 | * waiting (in which case it goes to sleep). |
19 | */ | |
20 | ||
21 | #ifndef _ASM_IA64_RWSEM_H | |
22 | #define _ASM_IA64_RWSEM_H | |
23 | ||
24 | #include <linux/list.h> | |
25 | #include <linux/spinlock.h> | |
26 | ||
27 | #include <asm/intrinsics.h> | |
28 | ||
29 | /* | |
30 | * the semaphore definition | |
31 | */ | |
32 | struct rw_semaphore { | |
16592d26 | 33 | signed long count; |
1da177e4 LT |
34 | spinlock_t wait_lock; |
35 | struct list_head wait_list; | |
1da177e4 LT |
36 | }; |
37 | ||
16592d26 CL |
38 | #define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000) |
39 | #define RWSEM_ACTIVE_BIAS __IA64_UL_CONST(0x0000000000000001) | |
40 | #define RWSEM_ACTIVE_MASK __IA64_UL_CONST(0x00000000ffffffff) | |
41 | #define RWSEM_WAITING_BIAS -__IA64_UL_CONST(0x0000000100000000) | |
1da177e4 LT |
42 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS |
43 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
44 | ||
1da177e4 LT |
45 | #define __RWSEM_INITIALIZER(name) \ |
46 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 47 | LIST_HEAD_INIT((name).wait_list) } |
1da177e4 LT |
48 | |
49 | #define DECLARE_RWSEM(name) \ | |
50 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
51 | ||
52 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
53 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
54 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
55 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
56 | ||
57 | static inline void | |
58 | init_rwsem (struct rw_semaphore *sem) | |
59 | { | |
60 | sem->count = RWSEM_UNLOCKED_VALUE; | |
61 | spin_lock_init(&sem->wait_lock); | |
62 | INIT_LIST_HEAD(&sem->wait_list); | |
1da177e4 LT |
63 | } |
64 | ||
65 | /* | |
66 | * lock for reading | |
67 | */ | |
68 | static inline void | |
69 | __down_read (struct rw_semaphore *sem) | |
70 | { | |
16592d26 | 71 | long result = ia64_fetchadd8_acq((unsigned long *)&sem->count, 1); |
1da177e4 LT |
72 | |
73 | if (result < 0) | |
74 | rwsem_down_read_failed(sem); | |
75 | } | |
76 | ||
77 | /* | |
78 | * lock for writing | |
79 | */ | |
80 | static inline void | |
81 | __down_write (struct rw_semaphore *sem) | |
82 | { | |
16592d26 | 83 | long old, new; |
1da177e4 LT |
84 | |
85 | do { | |
86 | old = sem->count; | |
87 | new = old + RWSEM_ACTIVE_WRITE_BIAS; | |
88 | } while (cmpxchg_acq(&sem->count, old, new) != old); | |
89 | ||
90 | if (old != 0) | |
91 | rwsem_down_write_failed(sem); | |
92 | } | |
93 | ||
94 | /* | |
95 | * unlock after reading | |
96 | */ | |
97 | static inline void | |
98 | __up_read (struct rw_semaphore *sem) | |
99 | { | |
16592d26 | 100 | long result = ia64_fetchadd8_rel((unsigned long *)&sem->count, -1); |
1da177e4 LT |
101 | |
102 | if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0) | |
103 | rwsem_wake(sem); | |
104 | } | |
105 | ||
106 | /* | |
107 | * unlock after writing | |
108 | */ | |
109 | static inline void | |
110 | __up_write (struct rw_semaphore *sem) | |
111 | { | |
16592d26 | 112 | long old, new; |
1da177e4 LT |
113 | |
114 | do { | |
115 | old = sem->count; | |
116 | new = old - RWSEM_ACTIVE_WRITE_BIAS; | |
117 | } while (cmpxchg_rel(&sem->count, old, new) != old); | |
118 | ||
119 | if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0) | |
120 | rwsem_wake(sem); | |
121 | } | |
122 | ||
123 | /* | |
124 | * trylock for reading -- returns 1 if successful, 0 if contention | |
125 | */ | |
126 | static inline int | |
127 | __down_read_trylock (struct rw_semaphore *sem) | |
128 | { | |
16592d26 | 129 | long tmp; |
1da177e4 LT |
130 | while ((tmp = sem->count) >= 0) { |
131 | if (tmp == cmpxchg_acq(&sem->count, tmp, tmp+1)) { | |
132 | return 1; | |
133 | } | |
134 | } | |
135 | return 0; | |
136 | } | |
137 | ||
138 | /* | |
139 | * trylock for writing -- returns 1 if successful, 0 if contention | |
140 | */ | |
141 | static inline int | |
142 | __down_write_trylock (struct rw_semaphore *sem) | |
143 | { | |
16592d26 | 144 | long tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE, |
1da177e4 LT |
145 | RWSEM_ACTIVE_WRITE_BIAS); |
146 | return tmp == RWSEM_UNLOCKED_VALUE; | |
147 | } | |
148 | ||
149 | /* | |
150 | * downgrade write lock to read lock | |
151 | */ | |
152 | static inline void | |
153 | __downgrade_write (struct rw_semaphore *sem) | |
154 | { | |
16592d26 | 155 | long old, new; |
1da177e4 LT |
156 | |
157 | do { | |
158 | old = sem->count; | |
159 | new = old - RWSEM_WAITING_BIAS; | |
160 | } while (cmpxchg_rel(&sem->count, old, new) != old); | |
161 | ||
162 | if (old < 0) | |
163 | rwsem_downgrade_wake(sem); | |
164 | } | |
165 | ||
166 | /* | |
167 | * Implement atomic add functionality. These used to be "inline" functions, but GCC v3.1 | |
168 | * doesn't quite optimize this stuff right and ends up with bad calls to fetchandadd. | |
169 | */ | |
16592d26 CL |
170 | #define rwsem_atomic_add(delta, sem) atomic64_add(delta, (atomic64_t *)(&(sem)->count)) |
171 | #define rwsem_atomic_update(delta, sem) atomic64_add_return(delta, (atomic64_t *)(&(sem)->count)) | |
1da177e4 | 172 | |
eb92f4ef RVR |
173 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
174 | { | |
175 | return (sem->count != 0); | |
176 | } | |
177 | ||
1da177e4 | 178 | #endif /* _ASM_IA64_RWSEM_H */ |