linux-kernel - Re: Threaded interrupt handlers broken?

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Date:	Sun, 16 Aug 2009 23:28:37 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Michael Buesch <mb@...sch.de>
cc:	linux-kernel@...r.kernel.org
Subject: Re: Threaded interrupt handlers broken?

On Sun, 16 Aug 2009, Michael Buesch wrote:
> On Sunday 16 August 2009 22:05:59 Thomas Gleixner wrote:
> > Hmm. Nothing interesting AFAICT, but it would be really interesting to
> > find out why the IRQ_DISABLED flag is set.
> > 
> > Can you add some debug into disable_irq() e.g. WARN_ON(irq ==
> > BC43_IRQ_NR); so we can see what disables that interrupt.
> 
> I do not see a warning, if I put this into __disable_irq():
> WARN_ON(irq == 52);
> /proc/interrupts shows 52 as IRQ number for b43.
> And dmesg shows "... irq 52 on host ... mapped to virtual irq 52".
> So I guess the test is OK and the flag is added by some other means.
> Maybe by some weird powerpc architecture code?
> 
> It seems a little bit weird, however, that the WARN_ON does not even trigger
> on module unload, which as far as I can tell should disable the IRQ line
> in the free_irq() call (no other shared devices on this IRQ).

free_irq does not call disable_irq().

There are only a few places which set that flag.

dynamic_irq_init() which should not be called in your system

__set_irq_handler() only if a handler gets uninstalled and replaced by
handle_bad_irq

__disable_irq() which you already excluded

__freq_irq() which should not be called

note_interrupt() which should be visible in dmesg, but we do not see
such a thing.

IRQ_DISABLED is cleared at even less places:

request_irq() and __enable_irq() 

I'm really confused. Can you please add debug into those places and
provide the output. Also please print desc->status of irq 52 before
and after calling request_threaded_irq().

Thanks,

	tglx







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