ROSSIER Daniel wrote: > Just to stimulate some discussions, I tried to bring some pieces of > answers. > > > -----Original Message----- From: [EMAIL PROTECTED] on > behalf of ROSSIER Daniel Sent: Fri 3/24/2006 4:38 PM To: > email@example.com Subject: [Xenomai-core] Timer IRQ propagation > > > > Hi, > > > > We have some doubts about how the things work between i-pipe & > xenomai regarding the timer. > > > > 1- First, when Xenomai is registered, the 10ms timer of Linux is > stolen by the Xenomai domain. How > > is the 10ms timer preserved? is it registered as a timer by the pod ? > > > >> Ok, silly question: the 10ms timer (or 1ms timer) is managed by >> Linux directly with its own list of timers; this doesn't affect >> Xenomai's timer list.
Under Xenomai, there is the host timer (nkpod-htimer) representing the Linux timer interrupt - with lowest prio and only propagated when the RT domain allows it. > > 2- When a timer IRQ is received, we understood that the IRQ is > ack'd and masked by handle_irq() and sent to the domains through > walk_pipeline() including Linux; but we have some doubts about that > since the timer ISR of Linux first acknowledges the interrupt, and it > seems that it acknowledges physically (hw ack); we expected that the > acknowledgement would be a virtual ack in the Linux domain since the > ack has been made previously by handle_irq(). In our case (ARM arch), > the ack actually corresponds to a mask and therefore the timer IRQ is > masked by Linux once it gets, and we then suspect some loss of timer > interrupts. > > have we understood correctly the mechanism? Any idea about this > behaviour? Is it normal? > > >> Still unclear to me; the ack would be done in the timer ISR; >> however in the (ARM) patch we have, ipipe performs a hardware ack; >> I've seen in the x86 patch that adeos makes nothing within >> __ipipe_ack_system_irq(). I guess the last behaviour is correct, >> isn't it? > That's something the ARM people here can better comment on. I would only say that physically ack'ing the shared timer IRQ twice or masking it under Linux would be a bug - if it actually happens this way. Jan
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