Re: perf/ftrace lockup on 3.12-rc6 with trigger code

From: Ingo Molnar
Date: Sat Oct 26 2013 - 04:49:03 EST

* Vince Weaver <vincent.weaver@xxxxxxxxx> wrote:

> I don't know if there are any better ways to try to debug things
> than the printk route. Though that has its own problems as the
> printk's themselves start showing up in the ftrace traces.

One additional brute-force method is earlyprintk=...,keep and
marking the (handful of) earlyprintk functions (and snprintf)
notrace, plus turning off printk itself completely.

That gives a completely instrumentation-free and locking-free
console output function of last resort :-/


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