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Date: Fri, 12 Sep 2014 10:26:26 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
cc: Jiang Liu <jiang.liu@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        x86@kernel.org
Subject: Re: Ask help about pre_init_apic_IRQ0()
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On Fri, 12 Sep 2014, Andy Shevchenko wrote:
> On Thu, 2014-09-11 at 23:59 +0200, Thomas Gleixner wrote:

> > > >      x86_intel_mid_timer=apbt_only
> 
> w/o patch
> 
> [    0.000000] Early APIC setup for system timer0
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: CPU: 0 PID: 0 at
> arch/x86/kernel/apic/apic.c:1393 setup_local_APIC+0x20c/0x2d9()
> 
> ...and stuck a bit later

Right, because there is no apbt timer in that machine and the
commandline tells the kernel to use it and ignore the local apic
timer.
 
> > > > or
> > > >      x86_intel_mid_timer=lapic_and_apbt
> > > 
> > > [    0.116858] BUG: unable to handle kernel NULL pointer dereference at
> > > 0000003a
> > > [    0.123820] IP: [<c1071c0e>] setup_irq+0xf/0x4d
> > > ...
> > > 
> 
> w/o patch
> 
> [    0.000000] Early APIC setup for system timer0
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: CPU: 0 PID: 0 at
> arch/x86/kernel/apic/apic.c:1393 setup_local_APIC+0x20c/0x2d9()
> 
> ...and boots normally

Right, because it uses the local apic timer later on.
 
Thanks for providing the data! I'll queue a removal of this mess.

Thanks,

	tglx