task interval in RTOS

The TI-RTOS kernel is a preemptive RTOS. The highest priority thread (Hwi, Swi, or Task) runs. What other threads do you have in the system? Are they higher priority and potentially running for a long time (and thus delaying other tasks). What is "task1" blocked on? Generally a task has the following structure

Void myTask(UArg arg0, UArg arg1)

{

    // setup code

    while (1) {

        // Block on a semaphore waiting for some action to post the semaphore and let the task run

        // or Task_sleep for some duration.

        // perform necessary actions

    }

The software is the EtherCAT example application.

There are two tasks with priority 6, two tasks with priority 8, one with priority 4 and my own task with priority 15.

From your RTOS description it sounds like it is not a really preemptive real time OS but a cooperative OS. In my understanding in a preemptive OS a task is stopped after consuming it's time slot and the next ready task is started. Here it seems that a task which loops forever such as while(1); can block the other tasks. Is this really true?

The TI-RTOS scheduler is not a time-sliced/round-robin. The highest priority thread that is ready to run will run until it completes (e.g. ISR ends or, for Tasks, hits a blocking call like Task_sleep or blocks on a semaphore).

From Wikipedia (en.wikipedia.org/.../Real-time_operating_system)

The most common designs are:

• Event-driven which switches tasks only when an event of higher priority needs servicing, called preemptive priority, or priority scheduling.
• Time-sharing designs switch tasks on a regular clocked interrupt, and on events, called round robin.

Yes, if you do while(1); in the highest priority task, no other tasks will ever run (Hwi and Swi threads will because they have higher priority than a Task).

Either a rtos clock or a general purpose timer hwi can be used to post a semaphore and wake up a task OR they can use Task_setPri() function to raise a tasks' priority to run. You should be able to achieve timeslicing in this way.