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Date: Thu, 2 May 2013 11:46:21 -0400
From: Dave Jones <davej@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: clockevents_program_event WARN_ON preventing boot.
Message-ID: <20130502154621.GA23990@redhat.com>
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	Thomas Gleixner <tglx@linutronix.de>,
	Linux Kernel <linux-kernel@vger.kernel.org>
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On Thu, May 02, 2013 at 12:37:26PM +0200, Thomas Gleixner wrote:

 > > On a second machine, I'm seeing an oops even earlier. As soon as I
 > > exit grub, I get a blinking cursor.  If I boot with earlyprintk=vga
 > > I can see..
 > > 
 > > Call Trace:
 > >  <IRQ>
 > >   tick_check_oneshot_broadcast
 > >   tick_check_idle
 > >   irq_enter
 > >   do_IRQ
 > >   common_interrupt
 > >  <EOI>
 > >   x86_64_start_reservations
 > >   x86_64_start_kernel
 > > RIP: clockevents_set_mode+0x18
 > > 
 > > Matching up the Code: line of the trace with the disassembly I see..
 > > 
 > >         if (dev->mode != mode) {
 > >  4c8:   39 77 38                cmp    %esi,0x38(%rdi)
 > > 
 > > 
 > 
 > diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
 > index 61d00a8..db9da73 100644
 > --- a/kernel/time/tick-broadcast.c
 > +++ b/kernel/time/tick-broadcast.c
 > @@ -475,7 +475,8 @@ void tick_check_oneshot_broadcast(int cpu)
 >  	if (cpumask_test_cpu(cpu, tick_broadcast_oneshot_mask)) {
 >  		struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
 >  
 > -		clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
 > +		if (td)
 > +			clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
 >  	}
 >  }
 >  

td must be non-null, because this doesn't change anything.

a clue: If I disable CONFIG_SLUB_DEBUG, or even boot with slub_debug=- then it boots fine.

I'll bisect.

	Dave

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