From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>,
Dave Jones <davej@redhat.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>, Paul Mackerras <paulus@samba.org>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: x86_pmu_start WARN_ON.
Date: Thu, 20 Feb 2014 16:54:16 +0100 [thread overview]
Message-ID: <20140220155416.GH9987@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <87r46xdbw4.fsf@tassilo.jf.intel.com>
On Thu, Feb 20, 2014 at 07:47:23AM -0800, Andi Kleen wrote:
> Peter Zijlstra <peterz@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.
next prev parent reply other threads:[~2014-02-20 15:54 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-30 19:02 x86_pmu_start WARN_ON Dave Jones
2014-02-10 21:26 ` Vince Weaver
2014-02-11 13:29 ` Peter Zijlstra
2014-02-12 21:04 ` Vince Weaver
2014-02-13 14:11 ` Vince Weaver
2014-02-13 17:35 ` Vince Weaver
2014-02-13 22:13 ` Vince Weaver
2014-02-17 15:28 ` Peter Zijlstra
2014-02-18 18:30 ` Vince Weaver
2014-02-18 22:20 ` Vince Weaver
2014-02-19 10:19 ` Peter Zijlstra
2014-02-19 22:34 ` Vince Weaver
2014-02-20 10:08 ` Peter Zijlstra
2014-02-20 15:47 ` Andi Kleen
2014-02-20 15:54 ` Peter Zijlstra [this message]
2014-02-20 17:31 ` Andi Kleen
2014-02-20 18:15 ` Peter Zijlstra
2014-02-20 18:23 ` Andi Kleen
2014-02-20 19:04 ` Steven Rostedt
2014-02-20 16:26 ` Steven Rostedt
2014-02-20 17:00 ` Peter Zijlstra
2014-02-20 17:43 ` Steven Rostedt
2014-02-20 17:46 ` Steven Rostedt
2014-02-20 18:18 ` Peter Zijlstra
2014-02-20 18:03 ` Vince Weaver
2014-02-20 18:23 ` Peter Zijlstra
2014-02-20 18:54 ` Vince Weaver
2014-02-20 19:21 ` Vince Weaver
2014-02-20 19:46 ` Vince Weaver
2014-02-21 14:37 ` Vince Weaver
2014-02-21 15:03 ` Peter Zijlstra
2014-02-21 20:18 ` Vince Weaver
2014-02-24 11:28 ` Peter Zijlstra
2014-02-26 5:59 ` Vince Weaver
2014-02-27 13:32 ` [tip:perf/core] perf/x86: Fix event scheduling tip-bot for Peter Zijlstra
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