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How ia vtaskYIELD related to TickISR ?

Posted by Angel Eyes on September 8, 2008
How are the functions taskdelay and taskyield related to tickISR ? I ask this question because , I am testing a port for Samsung S3C4510 on skyeye simulator , it in turn runs on cygwin .

Free running the tasks works fine , but calling any of the above mentioned functions suspends the tasks indefinitely . Either the TickISR is getting blocked on the simulator due to the function call to taskyield or taskdelay or something else is happening , thats what I suspect . Has anyone seen such an occurence ?

RE: How ia vtaskYIELD related to TickISR ?

Posted by Richard on September 8, 2008
When a task blocks using vTaskDelay() the block time is added to the current tick time to generate a time at which the task should wait. Then in the tick interrupt after updating the tick time the new time value is compared against the wake time of the blocked tasks. If the wake time has been reached the blocked task is unblocked.

Are you sure the tick interrupt is working? Sometimes in simulators only the core is simulated, not peripherals such as timers.


RE: How ia vtaskYIELD related to TickISR ?

Posted by Angel Eyes on September 8, 2008
Hi Richard ,

Thanks .

I have seen that timer0 interrupt gets generated with skyeye simulator . Even when I create 2 simple tasks , and start the scheduler i see that each of the tasks print out characters through the UART ( simulator output ) .

To make sure that the interrupt is invoked , I have added a line of code to output a string to the UART once it is in the ISR. I see for the free running of the task , the context switch happens after the ISR is entered.

However on including the vTaskDelay or TaskYield API , the first task which is entered and reaches the taskyield or taskdelay suspends .

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