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Re: Preempted interrupt handler

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Preempted interrupt handler
From: Srinivas Kommu <kommu@hotmail.com>
Date: Wed, 21 Dec 2005 11:39:06 -0800
Cc: Yoann Allain <yallain@avilinks.com>, "'linux-mips@linux-mips.org'" <linux-mips@linux-mips.org>
In-reply-to: <20051220131829.GB3376@linux-mips.org>
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References: <43A6F155.7080402@avilinks.com> <20051220131829.GB3376@linux-mips.org>
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On Tue, Dec 20, 2005 at 02:18:29PM +0100, Ralf Baechle wrote:
> On Mon, Dec 19, 2005 at 06:43:49PM +0100, Yoann Allain wrote:
> 
> > I'm actually working on a driver for a Marvell chip on a MIPS-based 
> > board running a 2.4 kernel. I have one problem:
> > In my module, my interrupt handler is never executed. I have traced the 
> > code until action->handler(irq, action->dev_id, regs)  in 
> > handle_IRQ_event() but when the handler should be executed, it is not 
> > and the kernel reenters in the low-level interrupt dispatch routine 
> > (because we're using level sensitive interrupts and it is still up). 
> > I've checked that the function pointer called is the one of my handler 
> > but my routine is never entered.
> > 
> > But when my handler is included in the kernel (ie not compiled as a 
> > module), it works! My function gets executed and acks the interrupt. In 
> > this case all goes fine.
> >
> > Moreover, I've noticed that the kernel symbols are mapped at adresses 
> > like 0x80258040 (start_kernel) but my module (and so is my handler) is 
> > loaded at something like 0xc000275c . I was thinking the module would be 
> > loaded in the same memory area as the kernel, so I think this is weird...
> > Perhaps, the module handler can't be executed because of its location 
> > but I don't know how to fix this.
> 
> Good new then - you don't need to fix anything :-)
> 
> The sympthoms you're describing are not specific enough, so only some
> general advice:
> 
>  - Make sure you're running a current version of modutils; older versions
>    have a number of bugs that could result in almost any kind of ill
>    behaviour.
>  - Make sure all object files of the modules have been built with
>    -mlong-calls.  That's done automatically by the kernel's makefiles
>    but not necessarily when building out of tree and certain versions
>    would silently tolerate the resulting relocation error.

Is it normal for the modules to be loaded at 0xc0000000 (this is
highmem, isn't it)? I see the same on my bcm1250 box. I've been wondering
why they can't be loaded in kseg0. Or is it because of bad
modutils/compiler flags?

thanks
srini

> 
>   Ralf

-- 
Srinivas Kommu
Cisco Systems, Inc.
Ph. (408) 527-8610

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