linux-kernel - Re: perf/tracepoint: another fuzzer generated lockup

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Message-ID: <20131115091521.3ad917fe@gandalf.local.home>
Date:	Fri, 15 Nov 2013 09:15:21 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Dave Jones <davej@...hat.com>
Subject: Re: perf/tracepoint: another fuzzer generated lockup

On Fri, 15 Nov 2013 13:28:33 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Fri, Nov 15, 2013 at 10:16:18AM +0900, Masami Hiramatsu wrote:
> > Kprobes itself can detect nested call by using per-cpu current-running
> > kprobe pointer. And if it is nested, it just skips calling handlers.
> > Anyway, I don't recommend to probe inside the handlers, but yes,
> > you can trace perf-handler by ftrace B). I actually traced a kprobe-bug
> > by kprobe-tracer last night, that was amazing :)
> 
> Ah, ok, so that would avoid the worst problems. Good. Should we still
> mark the entire perf swevent path as __kprobes just to be sure?

I wouldn't unless we can prove that it breaks. It's sometimes nice to
be able to debug the debugging facilities with the debugging
facilities ;-)

-- Steve
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