FreeRTOS实时操作系统临界段保护

#define taskENTER_CRITICAL()portENTER_CRITICAL()
#define taskEXIT_CRITICAL()portEXIT_CRITICAL()

#define portENTER_CRITICAL()vPortEnterCritical()
#define portEXIT_CRITICAL()vPortExitCritical()

//这个值用来记录中断嵌套次数，在调度器启动时会被重新初始化为0//vTaskStartScheduler()->xPortStartScheduler()->uxCriticalNesting = 0。static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;void vPortEnterCritical( void ){portDISABLE_INTERRUPTS();//关中断uxCriticalNesting++;__dsb( portSY_FULL_READ_WRITE );__isb( portSY_FULL_READ_WRITE );if( uxCriticalNesting == 1 ){configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );}}void vPortExitCritical( void ){configASSERT( uxCriticalNesting );uxCriticalNesting--;if( uxCriticalNesting == 0 ) //没有嵌套的话就可以开中断了{portENABLE_INTERRUPTS();}}//这个值用来记录中断嵌套次数，在调度器启动时会被重新初始化为0
//vTaskStartScheduler()->xPortStartScheduler()->uxCriticalNesting = 0。
static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
void vPortEnterCritical( void )
{
	portDISABLE_INTERRUPTS();//关中断
	uxCriticalNesting++;
	__dsb( portSY_FULL_READ_WRITE );
	__isb( portSY_FULL_READ_WRITE );
	if( uxCriticalNesting == 1 )
	{
		configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
	}
}
void vPortExitCritical( void )
{
	configASSERT( uxCriticalNesting );
	uxCriticalNesting--;
	if( uxCriticalNesting == 0 ) //没有嵌套的话就可以开中断了
	{
		portENABLE_INTERRUPTS();
	}
}

#define portDISABLE_INTERRUPTS()ulPortSetInterruptMask()
#define portENABLE_INTERRUPTS()vPortClearInterruptMask( 0 )

__asm uint32_t ulPortSetInterruptMask( void )
{
	PRESERVE8
	mrs r0, basepri  //r0作为函数返回值
	mov r1, #configMAX_SYSCALL_INTERRUPT_PRIORITY
	msr basepri, r1
	bx r14
}
/*-----------------------------------------------------------*/
__asm void vPortClearInterruptMask( uint32_t ulNewMask )
{
	PRESERVE8
	msr basepri, r0
	bx r14
}

#define taskENTER_CRITICAL_FROM_ISR() portSET_INTERRUPT_MASK_FROM_ISR()
#define taskEXIT_CRITICAL_FROM_ISR( x ) portCLEAR_INTERRUPT_MASK_FROM_ISR( x )

#define portSET_INTERRUPT_MASK_FROM_ISR()ulPortSetInterruptMask()
#define portCLEAR_INTERRUPT_MASK_FROM_ISR(x)vPortClearInterruptMask(x)