Date: Fri, 28 Feb 2014 14:23:28 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Vince Weaver <vincent.weaver@maine.edu>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>
Subject: Re: perf_fuzzer compiled for x32 causes reboot
Message-ID: <20140228222328.GN11910@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
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 <20140228205409.GB14089@laptop.programming.kicks-ass.net>
 <20140228211733.GK11910@linux.vnet.ibm.com>
 <20140228212700.GH14089@laptop.programming.kicks-ass.net>
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On Fri, Feb 28, 2014 at 05:05:53PM -0500, Steven Rostedt wrote:
> On Fri, 28 Feb 2014 22:55:11 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Fri, Feb 28, 2014 at 01:51:50PM -0800, Paul E. McKenney wrote:
> > > On Fri, Feb 28, 2014 at 10:27:00PM +0100, Peter Zijlstra wrote:
> > > > On Fri, Feb 28, 2014 at 01:17:33PM -0800, Paul E. McKenney wrote:
> > > > > This code isn't running in idle context is it?  If so, RCU will happily
> > > > > free out from under it.  CONFIG_PROVE_RCU should detect this sort of thing,
> > > > > though.
> > > > 
> > > > Well, interrupts/NMIs can happen when idle, but the interrupt/NMI
> > > > entry code deals with the idle state AFAIK.
> > > 
> > > Yep, rcu_irq_enter() and rcu_nmi_enter() deal with that.  More worried
> > > about this being code invoked from some energy-efficiency driver or
> > > another within the idle loop.
> > 
> > Right, so any tracepoint can end up there; but I thought there was
> > already the rule that tracepoints needed RCU enabled.
> 
> There is and we have special tracepoint caller for those cases we want a
> tracepoint out of RCU scope. These will reactivate rcu in the
> tracepoint code.
> 
>   trace_<tp_name>_rcuidle(...)

OK, I finally looked at the emails leading up to this in the thread...
I believe that I am doing premature debugging.

							Thanx, Paul

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