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SubjectRe: Linux 3.4 released
At Wed, 23 May 2012 13:26:57 -0700,
Tejun Heo wrote:
>
> Cc'ing Takashi. Hi!

Also Cc'ed Fengguang, who worked on ELD stuff.

> On Wed, May 23, 2012 at 09:56:36PM +0200, Jörg-Volker Peetz wrote:
> > May 23 21:32:33 hostname kernel: XXX delayed_work_timer_fn: cwq
> > (null), fn=hdmi_repoll_eld
>
> So, we have the winner.
>
> Takashi, sound/pci/hda/patch_hdmi.c::hdmi_repoll_eld() is causing
> workqueue code dereference %NULL pointer. It *looks* like something
> is corrupting the work item while it's queued. It could be a
> workqueue bug but I don't think that's likely - the code has been
> stable for quite some time now. I glanced through the code and
> nothing stands out. Does something ring a bell?

I also don't know of this problem. My initial thought was that the
work struct placed right after sink_eld in struct hdmi_spec_per_pin is
overwritten wrongly by reading some ELD data. But I failed to spot
out the bug...

Reading back through the thread, the problem seems triggered via usb
video cam. I wonder how this is connected to the HDMI audio.

To get things straight: does this bug happen even without HDMI, DP or
DVI cable plugged, i.e. only with the laptop without connecting to the
external digital output?


> > (without line-break).
> >
> > By the way, don't know if this is related, I have a phenomenon with a spurious
> > interrupt with every linux version I've used before on this notebook. Half a
> > minute after starting the system the computer produces approx. 220 lines like
> >
> > ... kernel: hda-intel: spurious response 0x0:0x0, last cmd=0x170503
> >
> > Now with 3.4.0, I see an additional message right before (the minute before) the
> > "XXX ..." line:
> >
> > ...kernel: hda_intel: azx_get_response timeout, switching to single_cmd mode:
> > last cmd=0x003f0900
>
> These too seem to be for you, Takashi. :)

This means essentially the codec communication got stalled. This is a
bad signal. It happens often with a wrong HD-audio verb, but often
with a bad IRQ, whatever.

I'd need alsa-info.sh output (run with --no-upload option) for further
analysis.


thanks,

Takashi
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