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Paul Mackerras09d4e0e2009-06-12 21:10:05 +00001/*
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>
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050016#include <linux/export.h>
Arun Sharma600634972011-07-26 16:09:06 -070017#include <linux/atomic.h>
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000018
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 */
31static union {
Shan Haif59ca052011-09-01 11:32:03 +080032 raw_spinlock_t lock;
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000033 char pad[L1_CACHE_BYTES];
Stephen Boydfcc16882012-12-19 23:39:48 -080034} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp = {
35 [0 ... (NR_LOCKS - 1)] = {
36 .lock = __RAW_SPIN_LOCK_UNLOCKED(atomic64_lock.lock),
37 },
38};
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000039
Yong Zhangcb475de2011-09-14 15:49:24 +080040static inline raw_spinlock_t *lock_addr(const atomic64_t *v)
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000041{
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
49long long atomic64_read(const atomic64_t *v)
50{
51 unsigned long flags;
Yong Zhangcb475de2011-09-14 15:49:24 +080052 raw_spinlock_t *lock = lock_addr(v);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000053 long long val;
54
Shan Haif59ca052011-09-01 11:32:03 +080055 raw_spin_lock_irqsave(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000056 val = v->counter;
Shan Haif59ca052011-09-01 11:32:03 +080057 raw_spin_unlock_irqrestore(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000058 return val;
59}
Roland Dreier3fc7b4b2009-07-29 15:04:02 -070060EXPORT_SYMBOL(atomic64_read);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000061
62void atomic64_set(atomic64_t *v, long long i)
63{
64 unsigned long flags;
Yong Zhangcb475de2011-09-14 15:49:24 +080065 raw_spinlock_t *lock = lock_addr(v);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000066
Shan Haif59ca052011-09-01 11:32:03 +080067 raw_spin_lock_irqsave(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000068 v->counter = i;
Shan Haif59ca052011-09-01 11:32:03 +080069 raw_spin_unlock_irqrestore(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000070}
Roland Dreier3fc7b4b2009-07-29 15:04:02 -070071EXPORT_SYMBOL(atomic64_set);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000072
Peter Zijlstra560cb122014-04-23 16:12:30 +020073#define ATOMIC64_OP(op, c_op) \
74void atomic64_##op(long long a, atomic64_t *v) \
75{ \
76 unsigned long flags; \
77 raw_spinlock_t *lock = lock_addr(v); \
78 \
79 raw_spin_lock_irqsave(lock, flags); \
80 v->counter c_op a; \
81 raw_spin_unlock_irqrestore(lock, flags); \
82} \
83EXPORT_SYMBOL(atomic64_##op);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000084
Peter Zijlstra560cb122014-04-23 16:12:30 +020085#define ATOMIC64_OP_RETURN(op, c_op) \
86long long atomic64_##op##_return(long long a, atomic64_t *v) \
87{ \
88 unsigned long flags; \
89 raw_spinlock_t *lock = lock_addr(v); \
90 long long val; \
91 \
92 raw_spin_lock_irqsave(lock, flags); \
93 val = (v->counter c_op a); \
94 raw_spin_unlock_irqrestore(lock, flags); \
95 return val; \
96} \
97EXPORT_SYMBOL(atomic64_##op##_return);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +000098
Peter Zijlstra560cb122014-04-23 16:12:30 +020099#define ATOMIC64_OPS(op, c_op) \
100 ATOMIC64_OP(op, c_op) \
101 ATOMIC64_OP_RETURN(op, c_op)
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000102
Peter Zijlstra560cb122014-04-23 16:12:30 +0200103ATOMIC64_OPS(add, +=)
104ATOMIC64_OPS(sub, -=)
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000105
Peter Zijlstra560cb122014-04-23 16:12:30 +0200106#undef ATOMIC64_OPS
107#undef ATOMIC64_OP_RETURN
108#undef ATOMIC64_OP
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000109
110long long atomic64_dec_if_positive(atomic64_t *v)
111{
112 unsigned long flags;
Yong Zhangcb475de2011-09-14 15:49:24 +0800113 raw_spinlock_t *lock = lock_addr(v);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000114 long long val;
115
Shan Haif59ca052011-09-01 11:32:03 +0800116 raw_spin_lock_irqsave(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000117 val = v->counter - 1;
118 if (val >= 0)
119 v->counter = val;
Shan Haif59ca052011-09-01 11:32:03 +0800120 raw_spin_unlock_irqrestore(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000121 return val;
122}
Roland Dreier3fc7b4b2009-07-29 15:04:02 -0700123EXPORT_SYMBOL(atomic64_dec_if_positive);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000124
125long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n)
126{
127 unsigned long flags;
Yong Zhangcb475de2011-09-14 15:49:24 +0800128 raw_spinlock_t *lock = lock_addr(v);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000129 long long val;
130
Shan Haif59ca052011-09-01 11:32:03 +0800131 raw_spin_lock_irqsave(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000132 val = v->counter;
133 if (val == o)
134 v->counter = n;
Shan Haif59ca052011-09-01 11:32:03 +0800135 raw_spin_unlock_irqrestore(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000136 return val;
137}
Roland Dreier3fc7b4b2009-07-29 15:04:02 -0700138EXPORT_SYMBOL(atomic64_cmpxchg);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000139
140long long atomic64_xchg(atomic64_t *v, long long new)
141{
142 unsigned long flags;
Yong Zhangcb475de2011-09-14 15:49:24 +0800143 raw_spinlock_t *lock = lock_addr(v);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000144 long long val;
145
Shan Haif59ca052011-09-01 11:32:03 +0800146 raw_spin_lock_irqsave(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000147 val = v->counter;
148 v->counter = new;
Shan Haif59ca052011-09-01 11:32:03 +0800149 raw_spin_unlock_irqrestore(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000150 return val;
151}
Roland Dreier3fc7b4b2009-07-29 15:04:02 -0700152EXPORT_SYMBOL(atomic64_xchg);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000153
154int atomic64_add_unless(atomic64_t *v, long long a, long long u)
155{
156 unsigned long flags;
Yong Zhangcb475de2011-09-14 15:49:24 +0800157 raw_spinlock_t *lock = lock_addr(v);
Luca Barbieri97577892010-03-01 19:55:47 +0100158 int ret = 0;
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000159
Shan Haif59ca052011-09-01 11:32:03 +0800160 raw_spin_lock_irqsave(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000161 if (v->counter != u) {
162 v->counter += a;
Luca Barbieri97577892010-03-01 19:55:47 +0100163 ret = 1;
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000164 }
Shan Haif59ca052011-09-01 11:32:03 +0800165 raw_spin_unlock_irqrestore(lock, flags);
Paul Mackerras09d4e0e2009-06-12 21:10:05 +0000166 return ret;
167}
Roland Dreier3fc7b4b2009-07-29 15:04:02 -0700168EXPORT_SYMBOL(atomic64_add_unless);