Here is a relevant part of the code

xSemaphoreHandle employee_signal = 0;

void employee_task() {

;

}

void boss(void *p){
for(;;){
LPC_printf("1\n\r");
xSemaphoreGive(employee_signal);
LPC_printf("3\r\n");
vTaskDelay(2000);

}
}


void employee(void *p){
for(;;){
if(xSemaphoreTake(employee_signal, portMAX_DELAY) == pdTRUE ){
employee_task();
LPC_printf("2\n\r");
}
}

}



int main (void) {

vSemaphoreCreateBinary(employee_signal);
LPC_UART0->IER = IER_THRE | IER_RLS;
SystemInit(); /* initialize clocks */
UARTInit(0, 38400);/* baud rate setting */
UARTInit(1, 38400);/* baud rate setting */
xTaskCreate( boss, ( signed char* ) "t1", 1024, NULL, 1, NULL );
xTaskCreate( employee, ( signed char* ) "t2", 1024, NULL, 1, NULL );
vTaskStartScheduler();
return 0;
}


I am expecting the boss task to start printing first, but as I can see, once immediately after the program starts the employee task is printing once to the console, then it falls into the right sequence. I am expecting the boss task to start instead, give a semaphore to the employee task and then the employee task to wake up. Pasting a part of the output here. This is on LPC1768 hardware, I hope I have configured the RTOS properly.


2 <- This should not be here
1 <- The printing should start from here
2
3
1
2
3
1
2
3

I am only able to avoid this situation id I am making the priority od the boss task higher. Then I am getting the correct output. How is the employee task printing first when the boss has not even started and given it a semaphore?

I am sorry, the topic should have been something else, like how can my task print even without getting a Semaphore?

The semaphore is created so the first take will pass. If you take the semaphore immediately after you create it (before your tasks start using it) then I think it will work the way your code expected it to.

Mutexes and binary semaphores are created in the already-given state, so the fact that your first take operation succeeds is expected behaviour.

For it to work as you want, you must take the semaphore immediately after creating it.