1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Generic UP xchg and cmpxchg using interrupt disablement. Does not 4 * support SMP. 5 */ 6 7 #ifndef __ASM_GENERIC_CMPXCHG_H 8 #define __ASM_GENERIC_CMPXCHG_H 9 10 #ifdef CONFIG_SMP 11 #error "Cannot use generic cmpxchg on SMP" 12 #endif 13 14 #include <linux/types.h> 15 #include <linux/irqflags.h> 16 17 /* 18 * This function doesn't exist, so you'll get a linker error if 19 * something tries to do an invalidly-sized xchg(). 20 */ 21 extern void __generic_xchg_called_with_bad_pointer(void); 22 23 static inline 24 unsigned long __generic_xchg(unsigned long x, volatile void *ptr, int size) 25 { 26 unsigned long ret, flags; 27 28 switch (size) { 29 case 1: 30 #ifdef __xchg_u8 31 return __xchg_u8(x, ptr); 32 #else 33 local_irq_save(flags); 34 ret = *(volatile u8 *)ptr; 35 *(volatile u8 *)ptr = x; 36 local_irq_restore(flags); 37 return ret; 38 #endif /* __xchg_u8 */ 39 40 case 2: 41 #ifdef __xchg_u16 42 return __xchg_u16(x, ptr); 43 #else 44 local_irq_save(flags); 45 ret = *(volatile u16 *)ptr; 46 *(volatile u16 *)ptr = x; 47 local_irq_restore(flags); 48 return ret; 49 #endif /* __xchg_u16 */ 50 51 case 4: 52 #ifdef __xchg_u32 53 return __xchg_u32(x, ptr); 54 #else 55 local_irq_save(flags); 56 ret = *(volatile u32 *)ptr; 57 *(volatile u32 *)ptr = x; 58 local_irq_restore(flags); 59 return ret; 60 #endif /* __xchg_u32 */ 61 62 #ifdef CONFIG_64BIT 63 case 8: 64 #ifdef __xchg_u64 65 return __xchg_u64(x, ptr); 66 #else 67 local_irq_save(flags); 68 ret = *(volatile u64 *)ptr; 69 *(volatile u64 *)ptr = x; 70 local_irq_restore(flags); 71 return ret; 72 #endif /* __xchg_u64 */ 73 #endif /* CONFIG_64BIT */ 74 75 default: 76 __generic_xchg_called_with_bad_pointer(); 77 return x; 78 } 79 } 80 81 #define generic_xchg(ptr, x) ({ \ 82 ((__typeof__(*(ptr))) \ 83 __generic_xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))); \ 84 }) 85 86 /* 87 * Atomic compare and exchange. 88 */ 89 #include <asm-generic/cmpxchg-local.h> 90 91 #define generic_cmpxchg_local(ptr, o, n) ({ \ 92 ((__typeof__(*(ptr)))__generic_cmpxchg_local((ptr), (unsigned long)(o), \ 93 (unsigned long)(n), sizeof(*(ptr)))); \ 94 }) 95 96 #define generic_cmpxchg64_local(ptr, o, n) \ 97 __generic_cmpxchg64_local((ptr), (o), (n)) 98 99 100 #ifndef arch_xchg 101 #define arch_xchg generic_xchg 102 #endif 103 104 #ifndef arch_cmpxchg_local 105 #define arch_cmpxchg_local generic_cmpxchg_local 106 #endif 107 108 #ifndef arch_cmpxchg64_local 109 #define arch_cmpxchg64_local generic_cmpxchg64_local 110 #endif 111 112 #define arch_cmpxchg arch_cmpxchg_local 113 #define arch_cmpxchg64 arch_cmpxchg64_local 114 115 #endif /* __ASM_GENERIC_CMPXCHG_H */ 116