linux-kernel - Re: [GIT PULL] tracing/kprobes: Add dynamic tracepoints + instruction decoder

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Date:	Thu, 27 Aug 2009 17:25:41 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Masami Hiramatsu <mhiramat@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [GIT PULL] tracing/kprobes: Add dynamic tracepoints +
	instruction decoder

On Thu, Aug 27, 2009 at 11:00:38AM -0400, Masami Hiramatsu wrote:
> Frederic Weisbecker wrote:
> > Ingo,
> > 
> > This is the kprobes tracing pile of patches. I've tested it
> > successfully by setting some kprobes through debugfs by hand.
> > 
> > It brings no known regressions.
> > 
> > However, the stress test provided by Masami have revealed some
> > unstable points. Some symbols are unsafe to probe and raise
> > probing recursion.
> > 
> > I've added a tiny patch in the series that helps identifying the
> > kprobe that has raised such situation.
> > For example it has learned me today that it's unsafe to trace
> > ret_from_exception() (obviously: it's on the int 3 handler path).
> 
> Thank you, Frederic.
> 
> I'm currently fixing those problems on x86-64 (on kvm).
> I'll also check it on x86-32, and fix it.
> 
> Thanks



Cool.
Don't hesitate to interate through small patches that fix these
sites.

So that I can continue to test it over time and report you what I find,
may be I can try to fix some of them too.

I haven't fixed ret_from_exception because I wasn't sure about the
right thing to do: putting it in the kprobes section or blacklist its
name. It's a bit more delicate to put assembly code into sections so... :)

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