Syslog question

[R Kimber]

On Wed, 15 Oct 2014 20:18:17 +0300
Marius Gedminas wrote:

> Definitely a bug somewhere in the kernel (or your hardware).  This
> volume of logging would be insane for normal use.

> Looks like this message is printed by sound/usb/mixer.c:
> https://github.com/torvalds/linux/blob/0429fbc0bdc297d64188483ba029a23773ae07b0/sound/usb/mixer.c#L2357
> 
> Do you have any USB sound devices plugged in?

Many thanks for your helpful reply.
Yes.  I have an MDAC that is connected by USB cable.

> Now about a workaround: these messages are printed using dev_dbg, which
> is described in http://lwn.net/Articles/434833/
> 
> Ubuntu is built with CONFIG_DYNAMIC_DEBUG=y, so you can turn each of
> these messages on and off separately.
> 
> In fact, they should be turned off at boot, according to that article.
> Have you done something to turn them on?

Not that I know of.  But without knowing how these are turned on/off I may
have done something that had that effect.  However I think this is unlikely
as I had this problem with my previous machine too, and doing the same
thing by accident, although possible, is not very likely.

> What is your Ubuntu version?  Your kernel version?

I'm running a clean install of 14.04 on a brand new PC. Kernel is
3.13.0-37-generic.  As far as I know, the MDAC follows USB 2.0 standards.

> What do you see if you run
> 
>   sudo grep 'status interrupt' /sys/kernel/debug/dynamic_debug/control

Running this returns nothing.

So, If I've understood the link you mentioned above, I need to add

echo -n 'file mixer.c line 2357 +p' >
       /sys/kernel/debug/dynamic_debug/control

to perhaps rc.local.  Is that right?

- Richard.
-- 
Richard Kimber