Philippe Gerum wrote:
This says that the interrupt will be ->end'ed at some later time (perhaps in the
interrupt handler task)
Jan Kiszka wrote:
Wolfgang Grandegger wrote:
Dmitry Adamushko wrote:
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:
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.
This says that the interrupt will eventually be ->end'ed by some later stage in
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.
ISR requests the interrupt dispatcher to re-enable the IRQ line upon
return (cumulable with HANDLED/CHAINED).
This says that the interrupt will be ->end'ed when this interrupt handler
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.
Sounds like RT_INTR_CHAINED, except that it's for the current pipeline stage?
Now for the quiz question (powerpc arch):
1. Assume an edge triggered interrupt
2. The RT-handler returns RT_INTR_ENABLE | RT_INTR_ENABLE (i.e. shared
interrupt, but no problem since it's edge-triggered)
3. Interrupt gets ->end'ed right after RT-handler has returned
4. Linux interrupt eventually handler starts its ->end() handler:
if (!(irq_desc[irq].status & (IRQ_DISABLED | IRQ_INPROGRESS)))
// Next interrupt occurs here!
Wouldn't this lead to a lost interrupt? Or am I overly paranoid?
My distinct feeling is that the return value should be a scalar and not a set!
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
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
Is this todo list accessible anywhere?
> 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.
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