use function "xTaskGetTickCount" in interrupt

Kernel
1

yukunduan wrote on Thursday, June 22, 2017:

In our porject,cpu is STM32F103 ,we use the function xTaskGetTickCount in the interrupt of canRx,but sometimes it can not return from the function “USB_LP_CAN1_RX0_IRQHandler”.Why and if we can use this function in the interrupt?It that ok?

2

yukunduan wrote on Thursday, June 22, 2017:

Also ,it will always dead in the interrupt of STM32F103,but it’s ok in STM32F407.

3

richarddamon wrote on Thursday, June 22, 2017:

The function doesn’t end if FromISR so it is not safe to use in an ISR. Depending on the port, sometimes it might work, or it might not.

4

heinbali01 wrote on Thursday, June 22, 2017:

A bit more precisely: it depends on portTICK_TYPE_IS_ATOMIC.

Look at the function:

TickType_t xTaskGetTickCount( void )
{
TickType_t xTicks;

	/* Critical section required if running on a 16 bit processor. */
	portTICK_TYPE_ENTER_CRITICAL();
	{
		xTicks = xTickCount;
	}
	portTICK_TYPE_EXIT_CRITICAL();

	return xTicks;
}

It may enter a critical section depending on portTICK_TYPE_IS_ATOMIC.

Suppose that xTickCount is a 32-bit variable, and suppose that the CPU is 32-bits, the copy will be “atomic”, and no protection is needed.
Your CPU, an STM32Fxxx is 32 bits, so it is safe to call xTaskGetTickCount().
Regards.