use function "xTaskGetTickCount" in interrupt

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?

yukunduan wrote on Thursday, June 22, 2017:

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

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.

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. */
		xTicks = xTickCount;

	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().