lib/string_helpers: introduce generic string_unescape
[linux-3.10.git] / lib / atomic64.c
1 /*
2  * Generic implementation of 64-bit atomics using spinlocks,
3  * useful on processors that don't have 64-bit atomic instructions.
4  *
5  * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version
10  * 2 of the License, or (at your option) any later version.
11  */
12 #include <linux/types.h>
13 #include <linux/cache.h>
14 #include <linux/spinlock.h>
15 #include <linux/init.h>
16 #include <linux/export.h>
17 #include <linux/atomic.h>
18
19 /*
20  * We use a hashed array of spinlocks to provide exclusive access
21  * to each atomic64_t variable.  Since this is expected to used on
22  * systems with small numbers of CPUs (<= 4 or so), we use a
23  * relatively small array of 16 spinlocks to avoid wasting too much
24  * memory on the spinlock array.
25  */
26 #define NR_LOCKS        16
27
28 /*
29  * Ensure each lock is in a separate cacheline.
30  */
31 static union {
32         raw_spinlock_t lock;
33         char pad[L1_CACHE_BYTES];
34 } atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
35         [0 ... (NR_LOCKS - 1)] = {
36                 .lock =  __RAW_SPIN_LOCK_UNLOCKED(atomic64_lock.lock),
37         },
38 };
39
40 static inline raw_spinlock_t *lock_addr(const atomic64_t *v)
41 {
42         unsigned long addr = (unsigned long) v;
43
44         addr >>= L1_CACHE_SHIFT;
45         addr ^= (addr >> 8) ^ (addr >> 16);
46         return &atomic64_lock[addr & (NR_LOCKS - 1)].lock;
47 }
48
49 long long atomic64_read(const atomic64_t *v)
50 {
51         unsigned long flags;
52         raw_spinlock_t *lock = lock_addr(v);
53         long long val;
54
55         raw_spin_lock_irqsave(lock, flags);
56         val = v->counter;
57         raw_spin_unlock_irqrestore(lock, flags);
58         return val;
59 }
60 EXPORT_SYMBOL(atomic64_read);
61
62 void atomic64_set(atomic64_t *v, long long i)
63 {
64         unsigned long flags;
65         raw_spinlock_t *lock = lock_addr(v);
66
67         raw_spin_lock_irqsave(lock, flags);
68         v->counter = i;
69         raw_spin_unlock_irqrestore(lock, flags);
70 }
71 EXPORT_SYMBOL(atomic64_set);
72
73 void atomic64_add(long long a, atomic64_t *v)
74 {
75         unsigned long flags;
76         raw_spinlock_t *lock = lock_addr(v);
77
78         raw_spin_lock_irqsave(lock, flags);
79         v->counter += a;
80         raw_spin_unlock_irqrestore(lock, flags);
81 }
82 EXPORT_SYMBOL(atomic64_add);
83
84 long long atomic64_add_return(long long a, atomic64_t *v)
85 {
86         unsigned long flags;
87         raw_spinlock_t *lock = lock_addr(v);
88         long long val;
89
90         raw_spin_lock_irqsave(lock, flags);
91         val = v->counter += a;
92         raw_spin_unlock_irqrestore(lock, flags);
93         return val;
94 }
95 EXPORT_SYMBOL(atomic64_add_return);
96
97 void atomic64_sub(long long a, atomic64_t *v)
98 {
99         unsigned long flags;
100         raw_spinlock_t *lock = lock_addr(v);
101
102         raw_spin_lock_irqsave(lock, flags);
103         v->counter -= a;
104         raw_spin_unlock_irqrestore(lock, flags);
105 }
106 EXPORT_SYMBOL(atomic64_sub);
107
108 long long atomic64_sub_return(long long a, atomic64_t *v)
109 {
110         unsigned long flags;
111         raw_spinlock_t *lock = lock_addr(v);
112         long long val;
113
114         raw_spin_lock_irqsave(lock, flags);
115         val = v->counter -= a;
116         raw_spin_unlock_irqrestore(lock, flags);
117         return val;
118 }
119 EXPORT_SYMBOL(atomic64_sub_return);
120
121 long long atomic64_dec_if_positive(atomic64_t *v)
122 {
123         unsigned long flags;
124         raw_spinlock_t *lock = lock_addr(v);
125         long long val;
126
127         raw_spin_lock_irqsave(lock, flags);
128         val = v->counter - 1;
129         if (val >= 0)
130                 v->counter = val;
131         raw_spin_unlock_irqrestore(lock, flags);
132         return val;
133 }
134 EXPORT_SYMBOL(atomic64_dec_if_positive);
135
136 long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n)
137 {
138         unsigned long flags;
139         raw_spinlock_t *lock = lock_addr(v);
140         long long val;
141
142         raw_spin_lock_irqsave(lock, flags);
143         val = v->counter;
144         if (val == o)
145                 v->counter = n;
146         raw_spin_unlock_irqrestore(lock, flags);
147         return val;
148 }
149 EXPORT_SYMBOL(atomic64_cmpxchg);
150
151 long long atomic64_xchg(atomic64_t *v, long long new)
152 {
153         unsigned long flags;
154         raw_spinlock_t *lock = lock_addr(v);
155         long long val;
156
157         raw_spin_lock_irqsave(lock, flags);
158         val = v->counter;
159         v->counter = new;
160         raw_spin_unlock_irqrestore(lock, flags);
161         return val;
162 }
163 EXPORT_SYMBOL(atomic64_xchg);
164
165 int atomic64_add_unless(atomic64_t *v, long long a, long long u)
166 {
167         unsigned long flags;
168         raw_spinlock_t *lock = lock_addr(v);
169         int ret = 0;
170
171         raw_spin_lock_irqsave(lock, flags);
172         if (v->counter != u) {
173                 v->counter += a;
174                 ret = 1;
175         }
176         raw_spin_unlock_irqrestore(lock, flags);
177         return ret;
178 }
179 EXPORT_SYMBOL(atomic64_add_unless);