1 /*
2 * Generic UP xchg and cmpxchg using interrupt disablement. Does not
3 * support SMP.
4 */
5
6 #ifndef __ASM_GENERIC_CMPXCHG_H
7 #define __ASM_GENERIC_CMPXCHG_H
8
9 #ifdef CONFIG_SMP
10 #error "Cannot use generic cmpxchg on SMP"
11 #endif
12
13 #include <linux/types.h>
14 #include <linux/irqflags.h>
15
16 #ifndef xchg
17
18 /*
19 * This function doesn't exist, so you'll get a linker error if
20 * something tries to do an invalidly-sized xchg().
21 */
22 extern void __xchg_called_with_bad_pointer(void);
23
24 static inline
__xchg(unsigned long x,volatile void * ptr,int size)25 unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
26 {
27 unsigned long ret, flags;
28
29 switch (size) {
30 case 1:
31 #ifdef __xchg_u8
32 return __xchg_u8(x, ptr);
33 #else
34 local_irq_save(flags);
35 ret = *(volatile u8 *)ptr;
36 *(volatile u8 *)ptr = x;
37 local_irq_restore(flags);
38 return ret;
39 #endif /* __xchg_u8 */
40
41 case 2:
42 #ifdef __xchg_u16
43 return __xchg_u16(x, ptr);
44 #else
45 local_irq_save(flags);
46 ret = *(volatile u16 *)ptr;
47 *(volatile u16 *)ptr = x;
48 local_irq_restore(flags);
49 return ret;
50 #endif /* __xchg_u16 */
51
52 case 4:
53 #ifdef __xchg_u32
54 return __xchg_u32(x, ptr);
55 #else
56 local_irq_save(flags);
57 ret = *(volatile u32 *)ptr;
58 *(volatile u32 *)ptr = x;
59 local_irq_restore(flags);
60 return ret;
61 #endif /* __xchg_u32 */
62
63 #ifdef CONFIG_64BIT
64 case 8:
65 #ifdef __xchg_u64
66 return __xchg_u64(x, ptr);
67 #else
68 local_irq_save(flags);
69 ret = *(volatile u64 *)ptr;
70 *(volatile u64 *)ptr = x;
71 local_irq_restore(flags);
72 return ret;
73 #endif /* __xchg_u64 */
74 #endif /* CONFIG_64BIT */
75
76 default:
77 __xchg_called_with_bad_pointer();
78 return x;
79 }
80 }
81
82 #define xchg(ptr, x) \
83 ((__typeof__(*(ptr))) __xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
84
85 #endif /* xchg */
86
87 /*
88 * Atomic compare and exchange.
89 *
90 * Do not define __HAVE_ARCH_CMPXCHG because we want to use it to check whether
91 * a cmpxchg primitive faster than repeated local irq save/restore exists.
92 */
93 #include <asm-generic/cmpxchg-local.h>
94
95 #define cmpxchg(ptr, o, n) cmpxchg_local((ptr), (o), (n))
96 #define cmpxchg64(ptr, o, n) cmpxchg64_local((ptr), (o), (n))
97
98 #endif /* __ASM_GENERIC_CMPXCHG_H */
99