Thread: [RTnet-users] Rtnet conceptual questions
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From: Shibu V. <vs...@cs...> - 2003-11-17 14:06:44
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Hey, I have a few basic questions of the priorities within rtnet applications: 1) Am I right in the assumption that rtnet.o has the network stack manager which runs as a RTAI real-time task. 2) If so what is its priority? RTAI real-time tasks have 0 as the highest priority. 3) rtnet.o must also have other co-operating real-time tasks. Right? What are their priorities? 4) Every real-time network driver must also run as a real-time task. But again with what priority? 5) What is the effect of loading many real-time tasks of high priorities on the operation of rtnet ? 6) What is the priority of rtmac? 7) What are the priorities of real-time applications based on rtnet? Regards Shibu Vachery |
From: Jan K. <ki...@rt...> - 2003-11-17 14:43:18
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Shibu Vachery schrieb: > Hey, > > I have a few basic questions of the priorities within rtnet applications: > > 1) Am I right in the assumption that rtnet.o has the network stack manager > which runs as a RTAI real-time task. > Yes, there is some kind of receive task running with prio 1 (it is called the stack manager) which passes incomming packets through the stack to the destination socket. > 2) If so what is its priority? RTAI real-time tasks have 0 as the highest > priority. > See above. > 3) rtnet.o must also have other co-operating real-time tasks. Right? > What are their priorities? > RTmac master (sends SOF) or client task (sends payload packets) run with prio 0. There is also a so called device manager task intended for error handling with prio 5, but this one is not used yet. > 4) Every real-time network driver must also run as a real-time task. But > again with what priority? > No, drivers do not need tasks. The transmission routine runs in the context of the sender (RTmac task or the application task if RTmac is not used). Incomming packets are first handled by the interrupt handler which then resumes (sem_signal) the stack manager task. > 5) What is the effect of loading many real-time tasks of high priorities > on the operation of rtnet ? > This can be critical in connection with RTmac. If the RTmac sender task is delayed too long, it may get out of sync and disturb other stations (collisions!). Reception is not that critical as time stamps are generated in the interrupt handler which can compensate delays. > 6) What is the priority of rtmac? > see above. > 7) What are the priorities of real-time applications based on rtnet? > Normally 2 or greater. I think, the examples use 10, but this first becomes important for real applications with more than just one task. Jan |