The STM32 ITM debug cell has channels to trace debug information in real time. Where would be the best place to insert a hook routine in FreeRTOS to output the task ID number to an ITM channel? This could provide task profiling information. It seems some IDE vendors already do this, sending task information to ITM channel 31.

One idea is to sample the active task in the system tick hook but this isn't very accurate since tasks can switch in less than the system tick interval depending on events.
Jack Peacock

This is exactly the reason that the trace hook macros were introduced - although they have been used for lots of things since then.

Take a look at http://www.freertos.org/rtos-trace-macros.html

If you just want to see which task is running when then all you need to do is define traceTASK_SWITCHED_IN to write the task ID out. If you want more information than that (for example, why a task gives up processing time) then you can define many more of the macros too.

If you come up with a comprehensive scheme for any particular IDE then it would be great if you posted it to the FreeRTOS Interactive section of the FreeRTOS site. http://interactive.freertos.org

Regards.