Tomas Kalibera wrote:
>
> Hi,
>
> I've noticed an interesting difference regarding primary and secondary
> domain runaway tasks. The primary domain ones are detected by Xenomai
> watchdog and terminated. The secondary domain ones are not terminated,
> but cause a system lockup, because a secondary domain task is always run
> in preference of other tasks (kernel complains by BUG: soft lockup -
> CPU#0 stuck for 11s!). Would there be a way to also detect the secondary
> domain runaway threads ? Since the kernel itself can do it, it should be
> possible, right ?
Yes, but if the Linux kernel does it, why would Xenomai reinvent the wheel ?
>
> Now, I've discovered that if I assign the secondary domain task priority
> 0, it would not lock up the system. 1 would, 99 would as well. What is
> the semantics ? Any secondary domain task with priority above zero runs
> in preference of any (non-Xenomai) Linux thread ?
This is not related to Xenomai, that is the semantic of SCHED_FIFO, also
called fixed priority scheduling.
>
> And asking from the other end, how to write polling (secondary domain)
> applications in Xenomai ? Should it have priority 0 ?
The best way to write polling applications with Xenomai is not to write
polling applications at all. Polling makes your processor burning hot,
does not scale well, and is a really poor programming style, really.
--
Gilles.
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