gistfile1.c

// workspace/visualizer/main.c 
void trace_task_switch(void *prev_task, unsigned int prev_tick, void *curr_task)
{
	char buf[128];
	int len = snprintf(buf, 128, "switch %d %d %d %d %d %d\n",
	                   prev_task, curr_task,
	                   xTaskGetTickCount(), get_reload(),
	                   prev_tick, get_current());
	write(logfile, buf, len);
}
// workspace/visuallizer/FreeRTOSConfig.h
// define an alias of trace_task_switch()
#define traceTASK_SWITCHED_IN() \
	if (pxPreviousTCB != pxCurrentTCB) { \
		trace_task_switch(pxPreviousTCB, \
		                  previous_systick_current, \
		                  pxCurrentTCB); \
	}

// workspace/freertos-basic/freertos/libraries/FreeRTOS/task.c
// vTaskSwitchCountext()
    /* Find the highest priority queue that contains ready tasks. */
	while( listLIST_IS_EMPTY( &( pxReadyTasksLists[ uxTopReadyPriority ] ) ) )
	{
		configASSERT( uxTopReadyPriority );
		--uxTopReadyPriority;
	}

	/* listGET_OWNER_OF_NEXT_ENTRY walks through the list, so the tasks of the
	same priority get an equal share of the processor time. */
	listGET_OWNER_OF_NEXT_ENTRY( pxCurrentTCB, &( pxReadyTasksLists[ uxTopReadyPriority ] ) );

	traceTASK_SWITCHED_IN();