On Thu, Feb 20, 2014 at 07:47:23AM -0800, Andi Kleen wrote: > Peter Zijlstra <pet...@infradead.org> writes: > > > On Wed, Feb 19, 2014 at 05:34:49PM -0500, Vince Weaver wrote: > >> So where would the NMI counter event get disabled? Would it never get > >> disabled, just because it's always running and always gets the same fixed > >> slot? Why isn't this a problem all the time, not just with corner cases? > > > > Well it could get another counter assignment I suppose; there's no > > guarantee it always ends up in the fixed counter although that's rather > > likely. > > > >> Is somehow n_added getting confused? > > > > I'd expect worse than a warning if that happened, but who knows. > > > > You could try with the below; make sure you've got CONFIG_FUNCTION_TRACER=y. > > > > Then (assuming debugfs is mounted in /debug ; most modern distros have > > it at /sys/kernel/debug but they're wrong!): > > > > # echo 0 > /debug/tracing/tracing_on > > # echo function > /debug/tracing/current_tracer > > # echo nop > /debug/tracing/current_tracer > > # echo 0 > /debug/tracing/trace > > # echo 1 > /debug/tracing/tracing_on > > > > And make it go *BOOM*, then: > > > > # cat /debug/tracing/trace | bzip2 -9 > ~/trace.bz2 > > This won't work unless you apply this patch > > http://lkml.org/lkml/2013/10/20/94
It will; trace_printk() works without -pg, I think you didn't read the instructions very well. And there's a very good reason not to apply your patch; you can route the function tracer into perf, guess what happens when perf calls the function tracer again :-) But yes; you can use it if you don't do that. But I didn't want the function trace, so who cares. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
