linux-kernel - Re: Threaded interrupt handlers broken?

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Message-ID: <20090904193749.GA1130@Chamillionaire.breakpoint.cc>
Date:	Fri, 4 Sep 2009 21:37:49 +0200
From:	Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
To:	Michael Buesch <mb@...sch.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org
Subject: Re: Threaded interrupt handlers broken?

* Michael Buesch | 2009-09-04 21:05:51 [+0200]:

>> 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.

The threaded interrupt infrastructure is okay as far as I can see it. My
currently OOT driver uses request_threaded_irq() and I can
modprobe/rmmod it with no problems. I just rebased it on top of -rc8 and
see no problems.

>Greetings, Michael.

Sebastian
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