STM32F4的原子操作怎么写？

王涛

void system_set_exec_alarm(uint8_t code) {
  uint8_t sreg = SREG;
  cli();
  sys_rt_exec_alarm = code;
  SREG = sreg;
}
上面的这个函数的意思是不是这样
把状态寄存器的数据保存到sreg这里。
然后关全局中断的函数cli();
变量赋值
还原状态寄存器的值
这个过程就是个 保存现场——执行原子操作——恢复现场 的过程，无论之前是否 I 置位，都不会发生错误或影响。
上面的函数是在AVR中实现的原子操作。
请问STM32F4中要实现这个操作怎么写

fengyunyu

http://bbs.21ic.com/icview-786350-1-1.html?source=1，LZ可以参考下

shangdawei

https://github.com/ARMmbed/mbed- ... orm/mbed_critical.h
https://github.com/ARMmbed/mbed- ... orm/mbed_critical.c

1. bool core_util_atomic_cas_u8(uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue)
   
2. {
   
3.     uint8_t currentValue = __LDREXB((volatile uint8_t*)ptr);
   
4.     if (currentValue != *expectedCurrentValue) {
   
5.         *expectedCurrentValue = currentValue;
   
6.         __CLREX();
   
7.         return false;
   
8.     }
   
9. 
   
10.     return !__STREXB(desiredValue, (volatile uint8_t*)ptr);
    
11. }
    
12. 
    
13. bool core_util_atomic_cas_u16(uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue)
    
14. {
    
15.     uint16_t currentValue = __LDREXH((volatile uint16_t*)ptr);
    
16.     if (currentValue != *expectedCurrentValue) {
    
17.         *expectedCurrentValue = currentValue;
    
18.         __CLREX();
    
19.         return false;
    
20.     }
    
21. 
    
22.     return !__STREXH(desiredValue, (volatile uint16_t*)ptr);
    
23. }
    
24. 
    
25. 
    
26. bool core_util_atomic_cas_u32(uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue)
    
27. {
    
28.     uint32_t currentValue = __LDREXW((volatile uint32_t*)ptr);
    
29.     if (currentValue != *expectedCurrentValue) {
    
30.         *expectedCurrentValue = currentValue;
    
31.         __CLREX();
    
32.         return false;
    
33.     }
    
34. 
    
35.     return !__STREXW(desiredValue, (volatile uint32_t*)ptr);
    
36. }
    
37. 
    
38. uint8_t core_util_atomic_incr_u8(uint8_t *valuePtr, uint8_t delta)
    
39. {
    
40.     uint8_t newValue;
    
41.     do {
    
42.         newValue = __LDREXB((volatile uint8_t*)valuePtr) + delta;
    
43.     } while (__STREXB(newValue, (volatile uint8_t*)valuePtr));
    
44.     return newValue;
    
45. }
    
46. 
    
47. uint16_t core_util_atomic_incr_u16(uint16_t *valuePtr, uint16_t delta)
    
48. {
    
49.     uint16_t newValue;
    
50.     do {
    
51.         newValue = __LDREXH((volatile uint16_t*)valuePtr) + delta;
    
52.     } while (__STREXH(newValue, (volatile uint16_t*)valuePtr));
    
53.     return newValue;
    
54. }
    
55. 
    
56. uint32_t core_util_atomic_incr_u32(uint32_t *valuePtr, uint32_t delta)
    
57. {
    
58.     uint32_t newValue;
    
59.     do {
    
60.         newValue = __LDREXW((volatile uint32_t*)valuePtr) + delta;
    
61.     } while (__STREXW(newValue, (volatile uint32_t*)valuePtr));
    
62.     return newValue;
    
63. }
    
64. 
    
65. 
    
66. uint8_t core_util_atomic_decr_u8(uint8_t *valuePtr, uint8_t delta)
    
67. {
    
68.     uint8_t newValue;
    
69.     do {
    
70.         newValue = __LDREXB((volatile uint8_t*)valuePtr) - delta;
    
71.     } while (__STREXB(newValue, (volatile uint8_t*)valuePtr));
    
72.     return newValue;
    
73. }
    
74. 
    
75. uint16_t core_util_atomic_decr_u16(uint16_t *valuePtr, uint16_t delta)
    
76. {
    
77.     uint16_t newValue;
    
78.     do {
    
79.         newValue = __LDREXH((volatile uint16_t*)valuePtr) - delta;
    
80.     } while (__STREXH(newValue, (volatile uint16_t*)valuePtr));
    
81.     return newValue;
    
82. }
    
83. 
    
84. uint32_t core_util_atomic_decr_u32(uint32_t *valuePtr, uint32_t delta)
    
85. {
    
86.     uint32_t newValue;
    
87.     do {
    
88.         newValue = __LDREXW((volatile uint32_t*)valuePtr) - delta;
    
89.     } while (__STREXW(newValue, (volatile uint32_t*)valuePtr));
    
90.     return newValue;
    
91. }

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