/* * Generic UP xchg and cmpxchg using interrupt disablement.  Does not * support SMP. */ #ifndef __ASM_GENERIC_CMPXCHG_H#define __ASM_GENERIC_CMPXCHG_H #ifdef CONFIG_SMP#error "Cannot use generic cmpxchg on SMP"#endif #include <linux/types.h>#include <linux/irqflags.h> #ifndef xchg /* * This function doesn't exist, so you'll get a linker error if * something tries to do an invalidly-sized xchg(). */extern void __xchg_called_with_bad_pointer(void); static inlineunsigned long __xchg(unsigned long x, volatile void *ptr, int size){	unsigned long ret, flags; 	switch (size) {	case 1:#ifdef __xchg_u8		return __xchg_u8(x, ptr);#else		local_irq_save(flags);		ret = *(volatile u8 *)ptr;		*(volatile u8 *)ptr = x;		local_irq_restore(flags);		return ret;#endif /* __xchg_u8 */ 	case 2:#ifdef __xchg_u16		return __xchg_u16(x, ptr);#else		local_irq_save(flags);		ret = *(volatile u16 *)ptr;		*(volatile u16 *)ptr = x;		local_irq_restore(flags);		return ret;#endif /* __xchg_u16 */ 	case 4:#ifdef __xchg_u32		return __xchg_u32(x, ptr);#else		local_irq_save(flags);		ret = *(volatile u32 *)ptr;		*(volatile u32 *)ptr = x;		local_irq_restore(flags);		return ret;#endif /* __xchg_u32 */ #ifdef CONFIG_64BIT	case 8:#ifdef __xchg_u64		return __xchg_u64(x, ptr);#else		local_irq_save(flags);		ret = *(volatile u64 *)ptr;		*(volatile u64 *)ptr = x;		local_irq_restore(flags);		return ret;#endif /* __xchg_u64 */#endif /* CONFIG_64BIT */ 	default:		__xchg_called_with_bad_pointer();		return x;	}} #define xchg(ptr, x) \	((__typeof__(*(ptr))) __xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))) #endif /* xchg */ /* * Atomic compare and exchange. * * Do not define __HAVE_ARCH_CMPXCHG because we want to use it to check whether * a cmpxchg primitive faster than repeated local irq save/restore exists. */#include <asm-generic/cmpxchg-local.h> #define cmpxchg(ptr, o, n)	cmpxchg_local((ptr), (o), (n))#define cmpxchg64(ptr, o, n)	cmpxchg64_local((ptr), (o), (n)) #endif /* __ASM_GENERIC_CMPXCHG_H */