Re: [Xenomai-help] What has highest priority RTcap or TDMA-synchronization reception?

[Jan Kiszka <jan.kiszka@domain.hid>]

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Benjamin Biegel wrote:
> Reading 'Life With Adeos' casts some light over the whole interrupt question. 
> However I have some further questions.
> 
> Why is it that the 'host interrupts' that you (Jan) mention below, can stall and 
> cause jitter in the xenomai threads, when the host interrupts have not been 
> given xenomai domain priorities? If such a host interrupt is played, Life With 
> Adeos makes it sound that this interrupt is preemptable, given an interrupt with 
> higher priority occurs.

Not sure what you mean with "stall", but even low-prio interrupts still
involve basic I-pipe activity to acknowledge and record them when they
first occur during high-prio Xenomai activities. And this can cause
(though small) disturbances to the real-time jobs.

> 
> Is it true that when RTcap is enabled, then every incoming frame will play an 
> interrupt of highest possible priority (real time nucleus), as to timestamp the 
> incoming frame?

This has nothing to do with RTcap, it is a property of RTnet NIC
drivers. Their RX interrupt handlers will run at high prio and perform
the timestamping. RTcap is just pushing all frames into Linux space for
collecting them via libpcap etc.

> 
> Is it true, that when a TDMA synchronization frame arrives, this will also play 
> an interrupt of highest possible priority (real time nucleus), as to calculate 
> the offset between local and global clock?

Same IRQ (or if there are >1 NIC: IRQ of identical priority) as above.

Jan


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