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Date: Mon, 19 May 2008 16:38:44 -0500
From: Scott Wood <scottwood@freescale.com>
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To: Rune Torgersen <runet@innovsys.com>
Subject: Re: Oops with PREEMPT-RT on 2.6.25.4
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Rune Torgersen wrote:
> Scott Wood wrote:
>> Almost certainly the latter.  Is the disk interrupt shared with any
>> other interrupts, that are marked IRQF_NODELAY?  The -rt
>> patch doesn't seem to handle mixing the two well.
> 
> Disk is on a muxed PCI interrupt. None of the other interrupts on the
> mux is fireing at the time.

Regardless of whether they're firing, any request_irq with IRQF_NODELAY 
will turn off threading for all handlers.

> Is is possible that the demuxer is not set up right? It is based loosely
> on pq2-pci-pic.c

Try calling irq_set_chip_and_handler() with handle_level_irq, rather 
than irq_set_chip().  The -rt patch doesn't seem to have threadified the 
  __do_IRQ() path.

-Scott