[PATCH] atomic: cmpxchg
[linux-3.10.git] / arch / sparc / lib / atomic32.c
1 /*
2  * atomic32.c: 32-bit atomic_t implementation
3  *
4  * Copyright (C) 2004 Keith M Wesolowski
5  * 
6  * Based on asm-parisc/atomic.h Copyright (C) 2000 Philipp Rumpf
7  */
8
9 #include <asm/atomic.h>
10 #include <linux/spinlock.h>
11 #include <linux/module.h>
12
13 #ifdef CONFIG_SMP
14 #define ATOMIC_HASH_SIZE        4
15 #define ATOMIC_HASH(a)  (&__atomic_hash[(((unsigned long)a)>>8) & (ATOMIC_HASH_SIZE-1)])
16
17 spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] = {
18         [0 ... (ATOMIC_HASH_SIZE-1)] = SPIN_LOCK_UNLOCKED
19 };
20
21 #else /* SMP */
22
23 static DEFINE_SPINLOCK(dummy);
24 #define ATOMIC_HASH_SIZE        1
25 #define ATOMIC_HASH(a)          (&dummy)
26
27 #endif /* SMP */
28
29 int __atomic_add_return(int i, atomic_t *v)
30 {
31         int ret;
32         unsigned long flags;
33         spin_lock_irqsave(ATOMIC_HASH(v), flags);
34
35         ret = (v->counter += i);
36
37         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
38         return ret;
39 }
40 EXPORT_SYMBOL(__atomic_add_return);
41
42 int atomic_cmpxchg(atomic_t *v, int old, int new)
43 {
44         int ret;
45         unsigned long flags;
46
47         spin_lock_irqsave(ATOMIC_HASH(v), flags);
48         ret = v->counter;
49         if (likely(ret == old))
50                 v->counter = new;
51
52         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
53         return ret;
54 }
55
56 void atomic_set(atomic_t *v, int i)
57 {
58         unsigned long flags;
59
60         spin_lock_irqsave(ATOMIC_HASH(v), flags);
61         v->counter = i;
62         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
63 }
64 EXPORT_SYMBOL(atomic_set);