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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
1da177e4 | 2 | /* |
7f30491c | 3 | * R/W semaphores for ia64 |
1da177e4 LT |
4 | * |
5 | * Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com> | |
6 | * Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com> | |
93e205a7 | 7 | * Copyright (C) 2005 Christoph Lameter <cl@linux.com> |
1da177e4 LT |
8 | * |
9 | * Based on asm-i386/rwsem.h and other architecture implementation. | |
10 | * | |
11 | * The MSW of the count is the negated number of active writers and | |
12 | * waiting lockers, and the LSW is the total number of active locks. | |
13 | * | |
14 | * The lock count is initialized to 0 (no active and no waiting lockers). | |
15 | * | |
16592d26 CL |
16 | * When a writer subtracts WRITE_BIAS, it'll get 0xffffffff00000001 for |
17 | * the case of an uncontended lock. Readers increment by 1 and see a positive | |
18 | * value when uncontended, negative if there are writers (and maybe) readers | |
1da177e4 LT |
19 | * waiting (in which case it goes to sleep). |
20 | */ | |
21 | ||
22 | #ifndef _ASM_IA64_RWSEM_H | |
23 | #define _ASM_IA64_RWSEM_H | |
24 | ||
bd807f9c RD |
25 | #ifndef _LINUX_RWSEM_H |
26 | #error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead." | |
27 | #endif | |
28 | ||
1da177e4 LT |
29 | #include <asm/intrinsics.h> |
30 | ||
16592d26 | 31 | #define RWSEM_UNLOCKED_VALUE __IA64_UL_CONST(0x0000000000000000) |
b680f097 TL |
32 | #define RWSEM_ACTIVE_BIAS (1L) |
33 | #define RWSEM_ACTIVE_MASK (0xffffffffL) | |
34 | #define RWSEM_WAITING_BIAS (-0x100000000L) | |
1da177e4 LT |
35 | #define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS |
36 | #define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS) | |
37 | ||
1da177e4 LT |
38 | /* |
39 | * lock for reading | |
40 | */ | |
41 | static inline void | |
42 | __down_read (struct rw_semaphore *sem) | |
43 | { | |
8ee62b18 | 44 | long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1); |
1da177e4 LT |
45 | |
46 | if (result < 0) | |
47 | rwsem_down_read_failed(sem); | |
48 | } | |
49 | ||
50 | /* | |
51 | * lock for writing | |
52 | */ | |
a02137eb MH |
53 | static inline long |
54 | ___down_write (struct rw_semaphore *sem) | |
1da177e4 | 55 | { |
16592d26 | 56 | long old, new; |
1da177e4 LT |
57 | |
58 | do { | |
8ee62b18 | 59 | old = atomic_long_read(&sem->count); |
1da177e4 | 60 | new = old + RWSEM_ACTIVE_WRITE_BIAS; |
8ee62b18 | 61 | } while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old); |
1da177e4 | 62 | |
a02137eb MH |
63 | return old; |
64 | } | |
65 | ||
66 | static inline void | |
67 | __down_write (struct rw_semaphore *sem) | |
68 | { | |
69 | if (___down_write(sem)) | |
1da177e4 LT |
70 | rwsem_down_write_failed(sem); |
71 | } | |
72 | ||
a02137eb MH |
73 | static inline int |
74 | __down_write_killable (struct rw_semaphore *sem) | |
75 | { | |
76 | if (___down_write(sem)) | |
77 | if (IS_ERR(rwsem_down_write_failed_killable(sem))) | |
78 | return -EINTR; | |
79 | ||
80 | return 0; | |
81 | } | |
82 | ||
1da177e4 LT |
83 | /* |
84 | * unlock after reading | |
85 | */ | |
86 | static inline void | |
87 | __up_read (struct rw_semaphore *sem) | |
88 | { | |
8ee62b18 | 89 | long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1); |
1da177e4 LT |
90 | |
91 | if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0) | |
92 | rwsem_wake(sem); | |
93 | } | |
94 | ||
95 | /* | |
96 | * unlock after writing | |
97 | */ | |
98 | static inline void | |
99 | __up_write (struct rw_semaphore *sem) | |
100 | { | |
16592d26 | 101 | long old, new; |
1da177e4 LT |
102 | |
103 | do { | |
8ee62b18 | 104 | old = atomic_long_read(&sem->count); |
1da177e4 | 105 | new = old - RWSEM_ACTIVE_WRITE_BIAS; |
8ee62b18 | 106 | } while (atomic_long_cmpxchg_release(&sem->count, old, new) != old); |
1da177e4 LT |
107 | |
108 | if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0) | |
109 | rwsem_wake(sem); | |
110 | } | |
111 | ||
112 | /* | |
113 | * trylock for reading -- returns 1 if successful, 0 if contention | |
114 | */ | |
115 | static inline int | |
116 | __down_read_trylock (struct rw_semaphore *sem) | |
117 | { | |
16592d26 | 118 | long tmp; |
8ee62b18 JL |
119 | while ((tmp = atomic_long_read(&sem->count)) >= 0) { |
120 | if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) { | |
1da177e4 LT |
121 | return 1; |
122 | } | |
123 | } | |
124 | return 0; | |
125 | } | |
126 | ||
127 | /* | |
128 | * trylock for writing -- returns 1 if successful, 0 if contention | |
129 | */ | |
130 | static inline int | |
131 | __down_write_trylock (struct rw_semaphore *sem) | |
132 | { | |
8ee62b18 JL |
133 | long tmp = atomic_long_cmpxchg_acquire(&sem->count, |
134 | RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS); | |
1da177e4 LT |
135 | return tmp == RWSEM_UNLOCKED_VALUE; |
136 | } | |
137 | ||
138 | /* | |
139 | * downgrade write lock to read lock | |
140 | */ | |
141 | static inline void | |
142 | __downgrade_write (struct rw_semaphore *sem) | |
143 | { | |
16592d26 | 144 | long old, new; |
1da177e4 LT |
145 | |
146 | do { | |
8ee62b18 | 147 | old = atomic_long_read(&sem->count); |
1da177e4 | 148 | new = old - RWSEM_WAITING_BIAS; |
8ee62b18 | 149 | } while (atomic_long_cmpxchg_release(&sem->count, old, new) != old); |
1da177e4 LT |
150 | |
151 | if (old < 0) | |
152 | rwsem_downgrade_wake(sem); | |
153 | } | |
154 | ||
1da177e4 | 155 | #endif /* _ASM_IA64_RWSEM_H */ |