Jan Kiszka wrote:
Wolfgang Grandegger wrote:

Hello,

Dmitry Adamushko wrote:

Hi,

this is the final set of patches against the SVN trunk of 2006-02-03.

It addresses mostly remarks concerning naming (XN_ISR_ISA ->
XN_ISR_EDGE), a few cleanups and updated comments.

Functionally, the support for shared interrupts (a few flags) to the


Not directly your fault: the increasing number of return flags for IRQ
handlers makes me worry that they are used correctly. I can figure out
what they mean (not yet that clearly from the docs), but does someone
else understand all this:

- RT_INTR_HANDLED

ISR says it has handled the IRQ, and does not want any propagation to take place down the pipeline. IOW, the IRQ processing stops there.

- RT_INTR_CHAINED

ISR says it wants the IRQ to be propagated down the pipeline. Nothing is said about the fact that the last ISR did or did not handle the IRQ locally; this is irrelevant.

- RT_INTR_ENABLE

ISR requests the interrupt dispatcher to re-enable the IRQ line upon return (cumulable with HANDLED/CHAINED).

- RT_INTR_NOINT


This new one comes from Dmitry's patch for shared IRQ support AFAICS. It would mean to continue processing the chain of handlers because the last ISR invoked was not concerned by the outstanding IRQ.

or

- RTDM_IRQ_PROPAGATE
- RTDM_IRQ_ENABLE
- RTDM_IRQ_NOINT

Third-party comments / suggestions welcome as well. Maybe I'm too
pessimistic.


rtdm (Jan's patch) and native skin.
In the later case, rt_intr_create() now contains the 6-th argument,
namely "int mode".

Now I'm waiting for the test results from Jan (the previous patch-set
remains to be suitable for testing too in case you are using it
already). Upon success, the new code is ready for merging.


Trying to manage the priority list of someone else is tricky - I hope we
can see something soon, but I cannot promise anything.


the patches have to be applied as follows :
- shirq-base
- shirq-v8
- shirq-proc
- shirq-edge
- shirq-ext

Happy testing ! :)

My concern is code size. I see that the patches add substantial amount
of code to the ISR. What about make this feature configurable?



I would vote for the (already scheduled?) extension to register an
optimised IRQ trampoline in case there is actually no sharing taking
place. This would also make the "if (irq == XNARCH_TIMER_IRQ)" path
obsolete.

I support that. Shared interrupts should be handled properly by Xeno since such - I'd say "last resort" - configuration could be needed; this said, we should not see this as the rule but rather as the exception, since this is basically required to solve some underlying hw limitations wrt interrupt management, and definitely has a significant cost on processing each shared IRQ wrt determinism.

Incidentally, there is an interesting optimization on the project's todo list that would allow non-RT interrupts to be masked at IC level when the Xenomai domain is active. We could do that on any arch with civilized interrupt management, and that would prevent any asynchronous diversion from the critical code when Xenomai is running RT tasks (kernel or user-space). Think of this as some hw-controlled interrupt shield. Since this feature requires to be able to individually mask each interrupt source at IC level, there should be no point in sharing fully vectored interrupts in such a configuration anyway. This fact also pleads for having the shared IRQ support as a build-time option.


Jan



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Philippe.

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