linux-kernel - Re: frequent softlockups with 3.10rc6.

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Date:	Wed, 26 Jun 2013 15:52:15 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dave Jones <davej@...hat.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrey Vagin <avagin@...nvz.org>
Subject: Re: frequent softlockups with 3.10rc6.

On Wed, 2013-06-26 at 01:23 -0400, Dave Jones wrote:
> 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@...ary:tracing)# cat trace
> # tracer: preemptirqsoff
> #
> (01:21:30:root@...ary:tracing)# 
> 

Did you apply the patch I added to my last email. It should have prevent
that form happening :-/

-- Steve


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