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Date: Tue, 27 Aug 2013 10:13:30 -0400
From: Dave Jones <davej@redhat.com>
To: David Ahern <dsahern@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, paulmck@linux.vnet.ibm.com,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: suspicious RCU usage (perf)
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On Tue, Aug 27, 2013 at 07:58:12AM -0600, David Ahern wrote:
 > On 8/27/13 7:10 AM, Steven Rostedt wrote:
 > > On Mon, 26 Aug 2013 15:49:24 -0400
 > > Dave Jones <davej@redhat.com> wrote:
 > >
 > >
 > >>   > Do you have /sys/kernel/debug with access permissions?
 > >>
 > >> Ah, yeah, that'll be it. Good catch.
 > >>
 > >> Sorry for the false alarm Steve ;)
 > >
 > > Yeah, but it still does not explain how perf got started. Perf requires
 > > a sys_perf_event_open() call to run.
 > 
 > Per Peter's response another option is the paranoia level:
 > 
 > # perf event paranoia level:
 > # -1 - not paranoid at all
 > #  0 - disallow raw tracepoint access for unpriv
 > #  1 - disallow cpu events for unpriv
 > #  2 - disallow kernel profiling for unpriv
 > kernel.perf_event_paranoid = -1

This I have set to 1 on that box. (The default)

	Dave