Thanks for your help,
My case is (2) - Low and high priority tasks in one application,
it's a video processing application with "Process" thread that must be finished ina desired time frame,
And the longlow priority task needs to work "only when time is available" ,
I need the ability to interupt it when new frame arrives.
I hoped that therewill bea solutioninsideTBB ,
i'll have to use something else to prioritze my threads.