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Date: Tue, 10 Apr 2012 10:50:14 +0200
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Subject: Re: i915_driver_irq_handler: irq 42: nobody cared [generic IRQ
 handling broken?]
From: Daniel Vetter <daniel@ffwll.ch>
To: Jiri Slaby <jslaby@suse.cz>
Cc: Chris Wilson <chris@chris-wilson.co.uk>, Jiri Slaby <jirislaby@gmail.com>,
        Keith Packard <keithp@keithp.com>, dri-devel@lists.freedesktop.org,
        LKML <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
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On Fri, Apr 6, 2012 at 23:31, Jiri Slaby <jslaby@suse.cz> wrote:
>> That was introduced in 05eff845a28499762075d3a72e238a31f4d2407c to close
>> a race where the pipestat triggered an interrupt after we processed the
>> secondary registers and before reseting the primary.
>>
>> But the basic premise that we should only enter the interrupt handler
>> with IIR!=0 holds (presuming non-shared interrupt lines such as MSI).
>
> Ok, this behavior is definitely new. I get several "nobody cared" about
> this interrupt a week. This never used to happen. And something weird
> emerges in /proc/interrupts when this happens:
>  42:    1003292    1212890   PCI-MSI-edge      �s����:0000:00:02.0
> instead of
>  42:    1006715    1218472   PCI-MSI-edge      i915@pci:0000:00:02.0

This looks ugly. Can you try to reproduce on 3.4-rc2? That should
contain everything that -next currently contains drm/i915-wise. If it
still happens there, please bisect it.

Also please check whether any of the subordinate interrupt regs
(pipestat) is stuck and might cause these interrupts as Jesse
suggested.

Thanks, Daniel
-- 
Daniel Vetter
daniel.vetter@ffwll.ch - +41 (0) 79 364 57 48 - http://blog.ffwll.ch