Re: frequent softlockups with 3.10rc6.

From: Dave Jones
Date: Wed Jun 26 2013 - 01:24:17 EST


On Tue, Jun 25, 2013 at 12:23:34PM -0400, Steven Rostedt wrote:

> Now, what we can try to do as well, is to add a trigger to disable
> tracing, which should (I need to check the code) stop tracing on printk.
> To do so:
>
> # echo printk:traceoff > /sys/kernel/debug/tracing/set_ftrace_filter
>
> This will add a trigger to the printk function that when called, will
> disable tracing. If it is hit before you get your trace, you can just
> re-enable tracing with:
>
> # echo 1 > /sys/kernel/debug/tracing/tracing_on
>
> Hmm, no it needs a fix to make this work. I applied a patch below that
> should do this correctly (and will put this into my 3.11 queue).
>
> If you run the test again with this change and with the above filter, it
> should stop the trace before overwriting the first dump, as it should
> ignore the printk output.

I think something isn't right with this patch.
After 10 hours, I hit the bug again, but...

(01:21:28:root@binary:tracing)# cat trace
# tracer: preemptirqsoff
#
(01:21:30:root@binary:tracing)#

Dave

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