linux-kernel - Re: Linux 3.4 released

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Date:	Fri, 25 May 2012 09:25:11 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Tejun Heo <tj@...nel.org>
Cc:	Fengguang Wu <fengguang.wu@...el.com>,
	Jörg-Volker Peetz <jvpeetz@....de>,
	linux-kernel@...r.kernel.org
Subject: Re: 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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