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Date: Tue, 18 Nov 2014 20:28:01 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
cc: Dave Jones <davej@redhat.com>, Linux Kernel <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        Don Zickus <dzickus@redhat.com>
Subject: Re: frequent lockups in 3.18rc4
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On Tue, 18 Nov 2014, Linus Torvalds wrote:
> On Tue, Nov 18, 2014 at 6:52 AM, Dave Jones <davej@redhat.com> wrote:
> >
> > Here's the first hit. Curiously, one cpu is missing.
> 
> That might be the CPU3 that isn't responding to IPIs due to some bug..
> 
> > NMI watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [trinity-c180:17837]
> > RIP: 0010:[<ffffffffa91a0db0>]  [<ffffffffa91a0db0>] bad_range+0x0/0x90
> 
> Hmm. Something looping in the page allocator? Not waiting for a lock,
> but livelocked? I'm not seeing anything here that should trigger the
> NMI watchdog at all.
> 
> Can the NMI watchdog get confused somehow?

That's the soft lockup detector which runs from the timer interrupt
not from NMI.
 
> So it does look like CPU3 is the problem, but sadly, CPU3 is
> apparently not listening, and doesn't even react to the NMI, much less

As I said in the other mail. It gets the NMI and reacts on it. It's
just mangled into the CPU0 backtrace. 

Thanks,

	tglx