[Xenomai-help] Interrupt handling vs. scheduler

["mau.salvi@domain.hid" <mau.salvi@domain.hid>]

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).

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?

Thanks in advance, bye



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