FreeRTOS临界段代码保护#

1
uint32_t save_status;
2
save_status = taskENTER_CRITICAL_FROM_ISR();
3
{
4
//临界区
5
}
6
taskEXIT_CRITICAL_FROM_ISR(save_status);
7
/*
8
- 保存状态：ulPortRaiseBASEPRI() 会：
9
  1.读取当前的 BASEPRI 寄存器值
10
  2.设置新的 BASEPRI 来屏蔽中断
11
  3.返回之前的中断状态（保存在 save_status 中）
12

13
- 恢复状态：taskEXIT_CRITICAL_FROM_ISR(save_status) 将之前保存的状态写回 BASEPRI
14
*/

1
/*开启*/
2
taskENTER_CRITICAL()
3
//1.
4
#define taskENTER_CRITICAL()               portENTER_CRITICAL()
5
//2.
6
#define portENTER_CRITICAL()               vPortEnterCritical()
7
//3.
8
void vPortEnterCritical( void )
9
{
10
    portDISABLE_INTERRUPTS();
11
    uxCriticalNesting++;
12
    /*初始化为0*/
13

14
  /* 这不是 enter critical 函数的中断安全版本，因此
15
  * assert（） 如果它是从中断上下文调用的。 仅限 API
16
  * 以“FromISR”结尾的函数可以在中断中使用。 仅在以下情况下断言
17
  * 临界嵌套计数为 1，以防止递归调用，如果
18
  * assert 函数也使用临界部分。*/
19
    if( uxCriticalNesting == 1 )
20
    {
21
        configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
22
    }
23
}
24
/*
25
每进入一次临界段，全局变量uxCriticalNesting都会加一
26
*/
27

28
//4.
29
#define portDISABLE_INTERRUPTS()              vPortRaiseBASEPRI()
30
//5.
31
    static portFORCE_INLINE void vPortRaiseBASEPRI( void )
32
    {
33
        uint32_t ulNewBASEPRI = configMAX_SYSCALL_INTERRUPT_PRIORITY;
34

35
        __asm
36
        {
37
            /* Set BASEPRI to the max syscall priority to effect a critical
38
             * section. */
39
      /* *INDENT-OFF* */
40
            msr basepri/*中断屏蔽寄存器*/, ulNewBASEPRI /*把ulNewBASEPRI给basepri*/
41
            dsb
42
            isb
43
      /* *INDENT-ON* */
44
        }
45
    }
46

47
//configMAX_SYSCALL_INTERRUPT_PRIORITY:
48
#define configMAX_SYSCALL_INTERRUPT_PRIORITY   ( configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )
49
#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY  5     /* 受FreeRTOS管理的中断最高优先级：5 */
50

51

52

53

54

55

56
/*关闭*/
57
taskEXIT_CRITICAL()
58
//1.
59
#define taskEXIT_CRITICAL()                portEXIT_CRITICAL()
60
//2.
61
#define portEXIT_CRITICAL()                vPortExitCritical()
62
//3.
63
void vPortExitCritical( void )
64
{
65
    configASSERT( uxCriticalNesting );
66
    uxCriticalNesting--;
67
    /*每调用一次退出临界段，uxCriticalNesting减一*/
68

69
    if( uxCriticalNesting == 0 )
70
    {
71
        /*只有当 uxCriticalNesting 为 0 的时候才会调用函数 portENABLE_INTERRUPTS()使能中断*/
72
        portENABLE_INTERRUPTS();
73
    }
74
}
75
//4.
76
#define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }  /* 断言失败时禁用中断并死循环 */
77
//5.
78
#define portENABLE_INTERRUPTS()                   vPortSetBASEPRI( 0 )
79
//6.
80
    static portFORCE_INLINE void vPortSetBASEPRI( uint32_t ulBASEPRI )
81
    {
82
        __asm
83
        {
84
            /* Barrier instructions are not used as this function is only used to
85
             * lower the BASEPRI value. */
86
/* *INDENT-OFF* */
87
            msr basepri, ulBASEPRI
88
/* *INDENT-ON* */
89
        }
90
    }

1
/*开启*/
2
taskENTER_CRITICAL_FROM_ISR();
3
//1.
4
#define taskENTER_CRITICAL_FROM_ISR()      portSET_INTERRUPT_MASK_FROM_ISR()
5
//2.
6
#define portSET_INTERRUPT_MASK_FROM_ISR()         ulPortRaiseBASEPRI()
7
//3.
8
    static portFORCE_INLINE uint32_t ulPortRaiseBASEPRI( void )
9
    {
10
        uint32_t ulReturn, ulNewBASEPRI = configMAX_SYSCALL_INTERRUPT_PRIORITY;
11

12
        __asm
13
        {
14
            /* Set BASEPRI to the max syscall priority to effect a critical
15
             * section. */
16
/* *INDENT-OFF* */
17
            mrs ulReturn, basepri /*把中断屏蔽寄存器首先提取出来*/
18
            msr basepri, ulNewBASEPRI /*把中断给关闭，写入后，所有优先级数值大于或等于 ulNewBASEPRI 的中断会被立即屏蔽*/
19
            dsb
20
            isb
21
/* *INDENT-ON* */
22
        }
23

24
        return ulReturn; /*返回*/
25
    } /*提取中断屏蔽寄存器的值（中断寄存器缺省值），把自己设置的值写入，所有优先级数值大于或等于 ulNewBASEPRI 的中断会被立即屏蔽*/
26
//4.
27
/* !!!! configMAX_SYSCALL_INTERRUPT_PRIORITY不能设置为零 !!!!
28
   参见http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
29
#define configMAX_SYSCALL_INTERRUPT_PRIORITY   ( configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )
30
#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY  5     /* 受FreeRTOS管理的中断最高优先级：5 */
31

32

33

34

35

36

37
/*关闭*/
38
taskEXIT_CRITICAL_FROM_ISR( x )
39
//1.
40
define taskEXIT_CRITICAL_FROM_ISR( x )    portCLEAR_INTERRUPT_MASK_FROM_ISR( x )
41
//2.
42
#define portCLEAR_INTERRUPT_MASK_FROM_ISR( x )    vPortSetBASEPRI( x )
43
//3.
44
    static portFORCE_INLINE void vPortSetBASEPRI( uint32_t ulBASEPRI )
45
    {
46
        __asm
47
        {
48
            /* Barrier instructions are not used as this function is only used to
49
             * lower the BASEPRI value. */
50
/* *INDENT-OFF* */
51
            msr basepri, ulBASEPRI /*恢复中断屏蔽寄存器的值*/
52
/* *INDENT-ON* */
53
        }
54
    }

1
uint32_t save_status1, save_status2, save_status3;
2

3
// 第一层嵌套
4
save_status1 = taskENTER_CRITICAL_FROM_ISR(); // BASEPRI = 0 -> 5, 返回 0
5
{
6
    // 第二层嵌套
7
    save_status2 = taskENTER_CRITICAL_FROM_ISR(); // BASEPRI = 5 -> 5, 返回 5
8
    {
9
        // 第三层嵌套
10
        save_status3 = taskENTER_CRITICAL_FROM_ISR(); // BASEPRI = 5 -> 5, 返回 5
11
        {
12
            // 临界区代码
13
        }
14
        taskEXIT_CRITICAL_FROM_ISR(save_status3); // BASEPRI = 5 -> 5
15
    }
16
    taskEXIT_CRITICAL_FROM_ISR(save_status2); // BASEPRI = 5 -> 5
17
}
18
taskEXIT_CRITICAL_FROM_ISR(save_status1); // BASEPRI = 5 -> 0 (完全恢复)