In the FreeRTOS.h file, there are lots of definition as shown in below:

#define traceTASK_INCREMENT_TICK( xTickCount )

the statement "#define traceTASKINCREMENTTICK( xTickCount )" seems actually doing nothing, I'm not quite understand it. Could anyone kindly help?

Look here in task.c :

~~~~ BaseTypet xTaskIncrementTick( void ) { TCBt * pxTCB; TickTypet xItemValue; BaseTypet xSwitchRequired = pdFALSE;

/* Called by the portable layer each time a tick interrupt occurs.
Increments the tick then checks to see if the new tick value will cause any
tasks to be unblocked. */
traceTASK_INCREMENT_TICK( xTickCount );
if( uxSchedulerSuspended == ( UBaseType_t ) pdFALSE )
...

~~~~

For every tick increment, it calls a macro or a function called traceTASK_INCREMENT_TICK().

By default, the macro does nothing:

~~~~

#define traceTASK_INCREMENT_TICK( xTickCount )

~~~~

Now if you want to do something during every tick-increment, you can define the macro in a new way. Write that new definition in you FreeRTOSConfig.h file, so it will be included before include/FreeRTOS.h.

~~~~ extern void vMyTickIncrement( TickType_t xCount );

do \
{ \
	vMyTickIncrement( xTickCount ); \
} while( 0 )

~~~~

When you run this, your function will be called for every increment.

So what you see in FreeRTOS is giving a proper default value for every macro.

Be careful: most trace-macro's are being called from critical situations. The task scheduler is often temporarily disabled, interrupts might have been disabled. When a trace macro is called from the idle task, there are many things you're not supposed to do, and the task-stack will be very small.

The good thing about trace macro's: they avoid the necessity to change the FreeRTOS source code. Regards.

That help me a lot, Thank you so much!