Date: Tue, 29 Nov 2016 07:10:04 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
        Vince Weaver <vincent.weaver@maine.edu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        "dvyukov@google.com" <dvyukov@google.com>
Subject: Re: perf: fuzzer BUG: KASAN: stack-out-of-bounds in __unwind_start
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On Tue, Nov 29, 2016 at 01:43:23PM +0100, Peter Zijlstra wrote:
> On Mon, Nov 28, 2016 at 11:52:41PM -0600, Josh Poimboeuf wrote:
> 
> > Did a little digging on git blame and found the following commit (which
> > seems to be the cause of the KASAN warning and missing stack dump):
> > 
> >   bc1dce514e9b ("rcu: Don't use NMIs to dump other CPUs' stacks")
> > 
> > I presume this commit is still needed because of the NMI printk deadlock
> > issues which were discussed at Kernel Summit.  I guess those issues need
> > to be sorted out before the above commit can be reverted.
> 
> Also, I most always run with these here patches applied:
> 
>   https://lkml.kernel.org/r/20161018170830.405990950@infradead.org
> 
> People are very busy polishing the turd we call printk, but from where
> I'm sitting its terminally and unfixably broken.
> 
> I should certainly add a revert of the above commit to the stack of
> patches I carry.

This isn't making me feel particularly confident about switching RCU
CPU stall warnings back to NMIs...  ;-)

							Thanx, Paul