Commit | Line | Data |
---|---|---|
70af2f8a WL |
1 | /* |
2 | * Queue read/write lock | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * (C) Copyright 2013-2014 Hewlett-Packard Development Company, L.P. | |
15 | * | |
16 | * Authors: Waiman Long <waiman.long@hp.com> | |
17 | */ | |
18 | #ifndef __ASM_GENERIC_QRWLOCK_H | |
19 | #define __ASM_GENERIC_QRWLOCK_H | |
20 | ||
21 | #include <linux/atomic.h> | |
22 | #include <asm/barrier.h> | |
23 | #include <asm/processor.h> | |
24 | ||
25 | #include <asm-generic/qrwlock_types.h> | |
26 | ||
27 | /* | |
28 | * Writer states & reader shift and bias | |
29 | */ | |
30 | #define _QW_WAITING 1 /* A writer is waiting */ | |
31 | #define _QW_LOCKED 0xff /* A writer holds the lock */ | |
32 | #define _QW_WMASK 0xff /* Writer mask */ | |
33 | #define _QR_SHIFT 8 /* Reader count shift */ | |
34 | #define _QR_BIAS (1U << _QR_SHIFT) | |
35 | ||
36 | /* | |
37 | * External function declarations | |
38 | */ | |
0e06e5be | 39 | extern void queued_read_lock_slowpath(struct qrwlock *lock, u32 cnts); |
f7d71f20 | 40 | extern void queued_write_lock_slowpath(struct qrwlock *lock); |
70af2f8a WL |
41 | |
42 | /** | |
f7d71f20 | 43 | * queued_read_can_lock- would read_trylock() succeed? |
70af2f8a WL |
44 | * @lock: Pointer to queue rwlock structure |
45 | */ | |
f7d71f20 | 46 | static inline int queued_read_can_lock(struct qrwlock *lock) |
70af2f8a WL |
47 | { |
48 | return !(atomic_read(&lock->cnts) & _QW_WMASK); | |
49 | } | |
50 | ||
51 | /** | |
f7d71f20 | 52 | * queued_write_can_lock- would write_trylock() succeed? |
70af2f8a WL |
53 | * @lock: Pointer to queue rwlock structure |
54 | */ | |
f7d71f20 | 55 | static inline int queued_write_can_lock(struct qrwlock *lock) |
70af2f8a WL |
56 | { |
57 | return !atomic_read(&lock->cnts); | |
58 | } | |
59 | ||
60 | /** | |
f7d71f20 | 61 | * queued_read_trylock - try to acquire read lock of a queue rwlock |
70af2f8a WL |
62 | * @lock : Pointer to queue rwlock structure |
63 | * Return: 1 if lock acquired, 0 if failed | |
64 | */ | |
f7d71f20 | 65 | static inline int queued_read_trylock(struct qrwlock *lock) |
70af2f8a WL |
66 | { |
67 | u32 cnts; | |
68 | ||
69 | cnts = atomic_read(&lock->cnts); | |
70 | if (likely(!(cnts & _QW_WMASK))) { | |
77e430e3 | 71 | cnts = (u32)atomic_add_return_acquire(_QR_BIAS, &lock->cnts); |
70af2f8a WL |
72 | if (likely(!(cnts & _QW_WMASK))) |
73 | return 1; | |
74 | atomic_sub(_QR_BIAS, &lock->cnts); | |
75 | } | |
76 | return 0; | |
77 | } | |
78 | ||
79 | /** | |
f7d71f20 | 80 | * queued_write_trylock - try to acquire write lock of a queue rwlock |
70af2f8a WL |
81 | * @lock : Pointer to queue rwlock structure |
82 | * Return: 1 if lock acquired, 0 if failed | |
83 | */ | |
f7d71f20 | 84 | static inline int queued_write_trylock(struct qrwlock *lock) |
70af2f8a WL |
85 | { |
86 | u32 cnts; | |
87 | ||
88 | cnts = atomic_read(&lock->cnts); | |
89 | if (unlikely(cnts)) | |
90 | return 0; | |
91 | ||
77e430e3 WD |
92 | return likely(atomic_cmpxchg_acquire(&lock->cnts, |
93 | cnts, cnts | _QW_LOCKED) == cnts); | |
70af2f8a WL |
94 | } |
95 | /** | |
f7d71f20 | 96 | * queued_read_lock - acquire read lock of a queue rwlock |
70af2f8a WL |
97 | * @lock: Pointer to queue rwlock structure |
98 | */ | |
f7d71f20 | 99 | static inline void queued_read_lock(struct qrwlock *lock) |
70af2f8a WL |
100 | { |
101 | u32 cnts; | |
102 | ||
77e430e3 | 103 | cnts = atomic_add_return_acquire(_QR_BIAS, &lock->cnts); |
70af2f8a WL |
104 | if (likely(!(cnts & _QW_WMASK))) |
105 | return; | |
106 | ||
107 | /* The slowpath will decrement the reader count, if necessary. */ | |
0e06e5be | 108 | queued_read_lock_slowpath(lock, cnts); |
70af2f8a WL |
109 | } |
110 | ||
111 | /** | |
f7d71f20 | 112 | * queued_write_lock - acquire write lock of a queue rwlock |
70af2f8a WL |
113 | * @lock : Pointer to queue rwlock structure |
114 | */ | |
f7d71f20 | 115 | static inline void queued_write_lock(struct qrwlock *lock) |
70af2f8a WL |
116 | { |
117 | /* Optimize for the unfair lock case where the fair flag is 0. */ | |
77e430e3 | 118 | if (atomic_cmpxchg_acquire(&lock->cnts, 0, _QW_LOCKED) == 0) |
70af2f8a WL |
119 | return; |
120 | ||
f7d71f20 | 121 | queued_write_lock_slowpath(lock); |
70af2f8a WL |
122 | } |
123 | ||
124 | /** | |
f7d71f20 | 125 | * queued_read_unlock - release read lock of a queue rwlock |
70af2f8a WL |
126 | * @lock : Pointer to queue rwlock structure |
127 | */ | |
f7d71f20 | 128 | static inline void queued_read_unlock(struct qrwlock *lock) |
70af2f8a WL |
129 | { |
130 | /* | |
131 | * Atomically decrement the reader count | |
132 | */ | |
77e430e3 | 133 | (void)atomic_sub_return_release(_QR_BIAS, &lock->cnts); |
70af2f8a WL |
134 | } |
135 | ||
70af2f8a | 136 | /** |
f7d71f20 | 137 | * queued_write_unlock - release write lock of a queue rwlock |
70af2f8a WL |
138 | * @lock : Pointer to queue rwlock structure |
139 | */ | |
f7d71f20 | 140 | static inline void queued_write_unlock(struct qrwlock *lock) |
70af2f8a | 141 | { |
2b2a85a4 | 142 | smp_store_release((u8 *)&lock->cnts, 0); |
70af2f8a | 143 | } |
70af2f8a WL |
144 | |
145 | /* | |
146 | * Remapping rwlock architecture specific functions to the corresponding | |
147 | * queue rwlock functions. | |
148 | */ | |
f7d71f20 WL |
149 | #define arch_read_can_lock(l) queued_read_can_lock(l) |
150 | #define arch_write_can_lock(l) queued_write_can_lock(l) | |
151 | #define arch_read_lock(l) queued_read_lock(l) | |
152 | #define arch_write_lock(l) queued_write_lock(l) | |
153 | #define arch_read_trylock(l) queued_read_trylock(l) | |
154 | #define arch_write_trylock(l) queued_write_trylock(l) | |
155 | #define arch_read_unlock(l) queued_read_unlock(l) | |
156 | #define arch_write_unlock(l) queued_write_unlock(l) | |
70af2f8a WL |
157 | |
158 | #endif /* __ASM_GENERIC_QRWLOCK_H */ |