linux-kernel - Re: Threaded interrupt handlers broken?

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Message-Id: <200909042135.38874.mb@bu3sch.de>
Date:	Fri, 4 Sep 2009 21:35:37 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Threaded interrupt handlers broken?

On Friday 04 September 2009 21:05:51 Michael Buesch wrote:
> On Friday 04 September 2009 20:55:52 Michael Buesch wrote:
> > On Monday 17 August 2009 14:30:31 Michael Buesch wrote:
> > > Also works. Thanks.
> > > 
> > > Tested-by: Michael Buesch <mb@...sch.de>
> > 
> > Hm, I've got a strange problem here related to threaded IRQs and rmmod.
> > 
> > If I do this sequence, it crashes the machine:
> > request_threaded_irq();
> > free_irq();
> > rmmod module
> > modprobe module
> > request_threaded_irq();
> > *boom*
> > 
> > Here are some oops messages. These are almost always different, so I
> > guess it crashes in IRQ context at random places when the IRQ triggers.
> > http://bu3sch.de/misc/irq_crash1.JPG
> > http://bu3sch.de/misc/irq_crash2.JPG
> > 
> > It seems to be a NULL pointer dereference somewhere, but I can't locate it.
> > Note that it does not happen, if I omit the rmmod.
> > 
> 
> Ok, what I see now is that the IRQ thread that belongs to the driver is not
> destroyed on free_irq(). So it is dangling and after rmmod/modprobe it will crash
> on interrupt, because the module is relocated.
> Bringing the device up and down several times (without reloading the module), which
> does several request_threaded_irq(); free_irq() sequences in a row, creates a new
> IRQ thread each time but does not destroy the old one.

Whoopsy, I think I messed up my driver and did not call free_irq(). Sorry for the noise. :(

-- 
Greetings, Michael.
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