linux-kernel - Re: Threaded interrupt handlers broken?

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Message-ID: <alpine.LFD.2.00.0908161516140.2782@localhost.localdomain>
Date:	Sun, 16 Aug 2009 15:19:03 +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:

> Hi,
> 

> I was trying to use threaded interrupt handlers, but the code always
> crashes within irq_thread() with a "BUG: spinlock bad magic
> 00000000".  The spinlock that's not properly initialized is from the
> wait_for_threads waitqueue.
>
> It crashes on line 526 (see below).  The initialization of the
> waitqueue struct seems to depend on whether the IRQ is shared or
> not. I don't know if that's correct, but I patched it to
> unconditionally initialize the struct. That did not help.

Hmm. The waitqueue is initialized when the first handler is set up. In
that case shared == 0. When the second handler is installed we do not
initialize it again as it is already initialized and even might have
waiters queued. I'll have a look.

Thanks,

	tglx
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