1 #ifndef ASM_X86_CMPXCHG_H 2 #define ASM_X86_CMPXCHG_H 3 4 #include <linux/compiler.h> 5 #include <asm/cpufeatures.h> 6 #include <asm/alternative.h> /* Provides LOCK_PREFIX */ 7 8 /* 9 * Non-existant functions to indicate usage errors at link time 10 * (or compile-time if the compiler implements __compiletime_error(). 11 */ 12 extern void __xchg_wrong_size(void) 13 __compiletime_error("Bad argument size for xchg"); 14 extern void __cmpxchg_wrong_size(void) 15 __compiletime_error("Bad argument size for cmpxchg"); 16 extern void __xadd_wrong_size(void) 17 __compiletime_error("Bad argument size for xadd"); 18 extern void __add_wrong_size(void) 19 __compiletime_error("Bad argument size for add"); 20 21 /* 22 * Constants for operation sizes. On 32-bit, the 64-bit size it set to 23 * -1 because sizeof will never return -1, thereby making those switch 24 * case statements guaranteeed dead code which the compiler will 25 * eliminate, and allowing the "missing symbol in the default case" to 26 * indicate a usage error. 27 */ 28 #define __X86_CASE_B 1 29 #define __X86_CASE_W 2 30 #define __X86_CASE_L 4 31 #ifdef CONFIG_64BIT 32 #define __X86_CASE_Q 8 33 #else 34 #define __X86_CASE_Q -1 /* sizeof will never return -1 */ 35 #endif 36 37 /* 38 * An exchange-type operation, which takes a value and a pointer, and 39 * returns the old value. 40 */ 41 #define __xchg_op(ptr, arg, op, lock) \ 42 ({ \ 43 __typeof__ (*(ptr)) __ret = (arg); \ 44 switch (sizeof(*(ptr))) { \ 45 case __X86_CASE_B: \ 46 asm volatile (lock #op "b %b0, %1\n" \ 47 : "+q" (__ret), "+m" (*(ptr)) \ 48 : : "memory", "cc"); \ 49 break; \ 50 case __X86_CASE_W: \ 51 asm volatile (lock #op "w %w0, %1\n" \ 52 : "+r" (__ret), "+m" (*(ptr)) \ 53 : : "memory", "cc"); \ 54 break; \ 55 case __X86_CASE_L: \ 56 asm volatile (lock #op "l %0, %1\n" \ 57 : "+r" (__ret), "+m" (*(ptr)) \ 58 : : "memory", "cc"); \ 59 break; \ 60 case __X86_CASE_Q: \ 61 asm volatile (lock #op "q %q0, %1\n" \ 62 : "+r" (__ret), "+m" (*(ptr)) \ 63 : : "memory", "cc"); \ 64 break; \ 65 default: \ 66 __ ## op ## _wrong_size(); \ 67 } \ 68 __ret; \ 69 }) 70 71 /* 72 * Note: no "lock" prefix even on SMP: xchg always implies lock anyway. 73 * Since this is generally used to protect other memory information, we 74 * use "asm volatile" and "memory" clobbers to prevent gcc from moving 75 * information around. 76 */ 77 #define xchg(ptr, v) __xchg_op((ptr), (v), xchg, "") 78 79 /* 80 * Atomic compare and exchange. Compare OLD with MEM, if identical, 81 * store NEW in MEM. Return the initial value in MEM. Success is 82 * indicated by comparing RETURN with OLD. 83 */ 84 #define __raw_cmpxchg(ptr, old, new, size, lock) \ 85 ({ \ 86 __typeof__(*(ptr)) __ret; \ 87 __typeof__(*(ptr)) __old = (old); \ 88 __typeof__(*(ptr)) __new = (new); \ 89 switch (size) { \ 90 case __X86_CASE_B: \ 91 { \ 92 volatile u8 *__ptr = (volatile u8 *)(ptr); \ 93 asm volatile(lock "cmpxchgb %2,%1" \ 94 : "=a" (__ret), "+m" (*__ptr) \ 95 : "q" (__new), "0" (__old) \ 96 : "memory"); \ 97 break; \ 98 } \ 99 case __X86_CASE_W: \ 100 { \ 101 volatile u16 *__ptr = (volatile u16 *)(ptr); \ 102 asm volatile(lock "cmpxchgw %2,%1" \ 103 : "=a" (__ret), "+m" (*__ptr) \ 104 : "r" (__new), "0" (__old) \ 105 : "memory"); \ 106 break; \ 107 } \ 108 case __X86_CASE_L: \ 109 { \ 110 volatile u32 *__ptr = (volatile u32 *)(ptr); \ 111 asm volatile(lock "cmpxchgl %2,%1" \ 112 : "=a" (__ret), "+m" (*__ptr) \ 113 : "r" (__new), "0" (__old) \ 114 : "memory"); \ 115 break; \ 116 } \ 117 case __X86_CASE_Q: \ 118 { \ 119 volatile u64 *__ptr = (volatile u64 *)(ptr); \ 120 asm volatile(lock "cmpxchgq %2,%1" \ 121 : "=a" (__ret), "+m" (*__ptr) \ 122 : "r" (__new), "0" (__old) \ 123 : "memory"); \ 124 break; \ 125 } \ 126 default: \ 127 __cmpxchg_wrong_size(); \ 128 } \ 129 __ret; \ 130 }) 131 132 #define __cmpxchg(ptr, old, new, size) \ 133 __raw_cmpxchg((ptr), (old), (new), (size), LOCK_PREFIX) 134 135 #define __sync_cmpxchg(ptr, old, new, size) \ 136 __raw_cmpxchg((ptr), (old), (new), (size), "lock; ") 137 138 #define __cmpxchg_local(ptr, old, new, size) \ 139 __raw_cmpxchg((ptr), (old), (new), (size), "") 140 141 #ifdef CONFIG_X86_32 142 # include <asm/cmpxchg_32.h> 143 #else 144 # include <asm/cmpxchg_64.h> 145 #endif 146 147 #define cmpxchg(ptr, old, new) \ 148 __cmpxchg(ptr, old, new, sizeof(*(ptr))) 149 150 #define sync_cmpxchg(ptr, old, new) \ 151 __sync_cmpxchg(ptr, old, new, sizeof(*(ptr))) 152 153 #define cmpxchg_local(ptr, old, new) \ 154 __cmpxchg_local(ptr, old, new, sizeof(*(ptr))) 155 156 /* 157 * xadd() adds "inc" to "*ptr" and atomically returns the previous 158 * value of "*ptr". 159 * 160 * xadd() is locked when multiple CPUs are online 161 */ 162 #define __xadd(ptr, inc, lock) __xchg_op((ptr), (inc), xadd, lock) 163 #define xadd(ptr, inc) __xadd((ptr), (inc), LOCK_PREFIX) 164 165 #define __cmpxchg_double(pfx, p1, p2, o1, o2, n1, n2) \ 166 ({ \ 167 bool __ret; \ 168 __typeof__(*(p1)) __old1 = (o1), __new1 = (n1); \ 169 __typeof__(*(p2)) __old2 = (o2), __new2 = (n2); \ 170 BUILD_BUG_ON(sizeof(*(p1)) != sizeof(long)); \ 171 BUILD_BUG_ON(sizeof(*(p2)) != sizeof(long)); \ 172 VM_BUG_ON((unsigned long)(p1) % (2 * sizeof(long))); \ 173 VM_BUG_ON((unsigned long)((p1) + 1) != (unsigned long)(p2)); \ 174 asm volatile(pfx "cmpxchg%c4b %2; sete %0" \ 175 : "=a" (__ret), "+d" (__old2), \ 176 "+m" (*(p1)), "+m" (*(p2)) \ 177 : "i" (2 * sizeof(long)), "a" (__old1), \ 178 "b" (__new1), "c" (__new2)); \ 179 __ret; \ 180 }) 181 182 #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \ 183 __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2) 184 185 #define cmpxchg_double_local(p1, p2, o1, o2, n1, n2) \ 186 __cmpxchg_double(, p1, p2, o1, o2, n1, n2) 187 188 #endif /* ASM_X86_CMPXCHG_H */ 189