Re: Kernel traces coming back with trash/clutter

From: Mark Hull-Richter
Date: Tue Apr 24 2007 - 20:01:45 EST

On 4/24/07, John Anthony Kazos Jr. <jakj@xxxxxxxxxxx> wrote:
> I am getting this odd content in the trace log (dmesg), and I cannot
> figure out what it is or why it is there.
> <7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7>
> <7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7>
> <7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7>
> <7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7><7>
> <7><7><7><7><7>__bio_add_page: 2x ph 88>=128 || hw 88>=88 || 360448>max
> ffffffff802525d8 generic_make_request(bio 000001017c745300) 50729472, 704

"<7>" is KERN_DEBUG in <include/linux/kernel.h>, used with printk. Are you
using printk in the following forms?

printk(KERN_DEBUG "A debug message.\n");

Yes, exclusively.

Perhaps you have something looping that's outputting KERN_DEBUG with a
null message? Or one of your diagnostic printk statements includes
KERN_DEBUG with no actual message?

No, they are all KERN_DEBUG<space>"some string here", almost all with
some formatted output as well. Could I be overloading the printk
output buffer, as in possibly too tightly repeated/looped code to be
able to output it all?

Remember, if you have a string in a variable without a KERN_*
prependation, you can do this.

printk(KERN_DEBUG "%s\n", debug_message);

Haven't tried that one - they're all of the form above.

Thanks again.

Mark Hull-Richter, Linux Kernel Engineer
DATAllegro (
85 Enterprise, Second Floor, Aliso Viejo, CA 92656
949-680-3082 - Office 949-330-7691 - fax
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