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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 | ||
bd807f9c RD |
24 | #ifndef _LINUX_RWSEM_H |
25 | #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead." | |
26 | #endif | |
27 | ||
1da177e4 LT |
28 | #include <linux/list.h> |
29 | #include <linux/spinlock.h> | |
30 | ||
31 | #include <asm/intrinsics.h> | |
32 | ||
33 | /* | |
34 | * the semaphore definition | |
35 | */ | |
36 | struct rw_semaphore { | |
16592d26 | 37 | signed long count; |
1da177e4 LT |
38 | spinlock_t wait_lock; |
39 | struct list_head wait_list; | |
1da177e4 LT |
40 | }; |
41 | ||
16592d26 CL |
42 | #define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000) |
43 | #define RWSEM_ACTIVE_BIAS __IA64_UL_CONST(0x0000000000000001) | |
44 | #define RWSEM_ACTIVE_MASK __IA64_UL_CONST(0x00000000ffffffff) | |
45 | #define RWSEM_WAITING_BIAS -__IA64_UL_CONST(0x0000000100000000) | |
1da177e4 LT |
46 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS |
47 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
48 | ||
1da177e4 LT |
49 | #define __RWSEM_INITIALIZER(name) \ |
50 | { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \ | |
61f4c3d6 | 51 | LIST_HEAD_INIT((name).wait_list) } |
1da177e4 LT |
52 | |
53 | #define DECLARE_RWSEM(name) \ | |
54 | struct rw_semaphore name = __RWSEM_INITIALIZER(name) | |
55 | ||
56 | extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem); | |
57 | extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem); | |
58 | extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem); | |
59 | extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem); | |
60 | ||
61 | static inline void | |
62 | init_rwsem (struct rw_semaphore *sem) | |
63 | { | |
64 | sem->count = RWSEM_UNLOCKED_VALUE; | |
65 | spin_lock_init(&sem->wait_lock); | |
66 | INIT_LIST_HEAD(&sem->wait_list); | |
1da177e4 LT |
67 | } |
68 | ||
69 | /* | |
70 | * lock for reading | |
71 | */ | |
72 | static inline void | |
73 | __down_read (struct rw_semaphore *sem) | |
74 | { | |
16592d26 | 75 | long result = ia64_fetchadd8_acq((unsigned long *)&sem->count, 1); |
1da177e4 LT |
76 | |
77 | if (result < 0) | |
78 | rwsem_down_read_failed(sem); | |
79 | } | |
80 | ||
81 | /* | |
82 | * lock for writing | |
83 | */ | |
84 | static inline void | |
85 | __down_write (struct rw_semaphore *sem) | |
86 | { | |
16592d26 | 87 | long old, new; |
1da177e4 LT |
88 | |
89 | do { | |
90 | old = sem->count; | |
91 | new = old + RWSEM_ACTIVE_WRITE_BIAS; | |
92 | } while (cmpxchg_acq(&sem->count, old, new) != old); | |
93 | ||
94 | if (old != 0) | |
95 | rwsem_down_write_failed(sem); | |
96 | } | |
97 | ||
98 | /* | |
99 | * unlock after reading | |
100 | */ | |
101 | static inline void | |
102 | __up_read (struct rw_semaphore *sem) | |
103 | { | |
16592d26 | 104 | long result = ia64_fetchadd8_rel((unsigned long *)&sem->count, -1); |
1da177e4 LT |
105 | |
106 | if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0) | |
107 | rwsem_wake(sem); | |
108 | } | |
109 | ||
110 | /* | |
111 | * unlock after writing | |
112 | */ | |
113 | static inline void | |
114 | __up_write (struct rw_semaphore *sem) | |
115 | { | |
16592d26 | 116 | long old, new; |
1da177e4 LT |
117 | |
118 | do { | |
119 | old = sem->count; | |
120 | new = old - RWSEM_ACTIVE_WRITE_BIAS; | |
121 | } while (cmpxchg_rel(&sem->count, old, new) != old); | |
122 | ||
123 | if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0) | |
124 | rwsem_wake(sem); | |
125 | } | |
126 | ||
127 | /* | |
128 | * trylock for reading -- returns 1 if successful, 0 if contention | |
129 | */ | |
130 | static inline int | |
131 | __down_read_trylock (struct rw_semaphore *sem) | |
132 | { | |
16592d26 | 133 | long tmp; |
1da177e4 LT |
134 | while ((tmp = sem->count) >= 0) { |
135 | if (tmp == cmpxchg_acq(&sem->count, tmp, tmp+1)) { | |
136 | return 1; | |
137 | } | |
138 | } | |
139 | return 0; | |
140 | } | |
141 | ||
142 | /* | |
143 | * trylock for writing -- returns 1 if successful, 0 if contention | |
144 | */ | |
145 | static inline int | |
146 | __down_write_trylock (struct rw_semaphore *sem) | |
147 | { | |
16592d26 | 148 | long tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE, |
1da177e4 LT |
149 | RWSEM_ACTIVE_WRITE_BIAS); |
150 | return tmp == RWSEM_UNLOCKED_VALUE; | |
151 | } | |
152 | ||
153 | /* | |
154 | * downgrade write lock to read lock | |
155 | */ | |
156 | static inline void | |
157 | __downgrade_write (struct rw_semaphore *sem) | |
158 | { | |
16592d26 | 159 | long old, new; |
1da177e4 LT |
160 | |
161 | do { | |
162 | old = sem->count; | |
163 | new = old - RWSEM_WAITING_BIAS; | |
164 | } while (cmpxchg_rel(&sem->count, old, new) != old); | |
165 | ||
166 | if (old < 0) | |
167 | rwsem_downgrade_wake(sem); | |
168 | } | |
169 | ||
170 | /* | |
171 | * Implement atomic add functionality. These used to be "inline" functions, but GCC v3.1 | |
172 | * doesn't quite optimize this stuff right and ends up with bad calls to fetchandadd. | |
173 | */ | |
16592d26 CL |
174 | #define rwsem_atomic_add(delta, sem) atomic64_add(delta, (atomic64_t *)(&(sem)->count)) |
175 | #define rwsem_atomic_update(delta, sem) atomic64_add_return(delta, (atomic64_t *)(&(sem)->count)) | |
1da177e4 | 176 | |
eb92f4ef RVR |
177 | static inline int rwsem_is_locked(struct rw_semaphore *sem) |
178 | { | |
179 | return (sem->count != 0); | |
180 | } | |
181 | ||
1da177e4 | 182 | #endif /* _ASM_IA64_RWSEM_H */ |