Re: [Xenomai-help] Interrupt handling vs. scheduler

[Philippe Gerum <rpm@xenomai.org>]

On Sun, 2010-12-12 at 19:47 +0100, mau.salvi@domain.hid wrote:
> Hello to all,
> 
> I observed a strange behaviour on oscilloscope during 
> interrupt handling when RT periodic tasks reschedule happens.
> 
> I have 
> an interrupt generated every 1ms by a PCI card: the interrupt was 
> handled into user-space with a RT task (priority 99) that sleeps on 
> rt_intr_wait(), and the handler was created with I_NOAUTOENA flag, so 
> there is a rt_intr_enable() call each cycle immediately before 
> rt_intr_wait(). Into my code there is another task that works 
> periodically on this PCI card data.
> 
> Due to a "slip" between PC and PCI 
> card hardware timers, sometimes there is an overlap between interrupt 
> handling and periodic task wakeup: in detail, during interrupt 
> handling, the periodic time for latter task expires, so wakeup must 
> take place. In this (and only in this) condition I observe a wrong call 
> to interrupt handling task immediately after the end of right handling: 
> so, I have two consecutive interrupt calls, as the expire timer signal 
> was delivered also to my interrupt handler. Task wakeup takes 
> regularily place.
> 
> This behaviour happens only if there is some other 
> periodic task into my executable: without that, interrupts was properly 
> handled every 1ms. "Strange" behaviour also happens if periodic task 
> does nothing (waits rescheduling only).

What is the return value of rt_intr_wait() in both the valid and
spurious cases?

> 
> I'm working on Ubuntu 10.04 
> x86 with Xenomai 2.5.5.2 on a vanilla kernel 2.6.35.7, Adeos patch 2.7-
> 04.
> Hardware:  Intel Celeron M 512 MHz processor, motherboard with SMI 
> services disabled by Xenomai at startup.
> 
> I've seen that a new Adeos 
> patch (2.8) was released for x86 arch, with more modifies into IRQ 
> code: does new patch fixes this problem?

We don't know which problem this could be the symptom of, yet.

> 
> Thanks in advance, bye
> 
> 
> 
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> 
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-- 
Philippe.