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Subject: Re: mmotm 2008-12-01-19-41: early exception (page fault -- deref
	of 0x20)
From: Matt Mackall <mpm@selenic.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Slaby <jirislaby@gmail.com>, linux-kernel@vger.kernel.org,
       arjan@linux.intel.com, tytso@mit.edu
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	 <20081202153336.7b765ec7.akpm@linux-foundation.org>
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Date: Tue, 02 Dec 2008 17:42:08 -0600
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On Tue, 2008-12-02 at 15:33 -0800, Andrew Morton wrote:
> On Wed, 03 Dec 2008 00:09:46 +0100
> Jiri Slaby <jirislaby@gmail.com> wrote:
> 
> > Hi,
> > 
> > while writing out warning about empty mtrr (or any other in the early stage),
> > I'm getting this:
> > PANIC: early exception 0e rip 10:ffffffff8025be26 error 0 cr2 20
> > Pid: 0, comm: swapper Not tainted 2.6.28-rc6-mm1_64 #484
> > Call Trace:
> >  [<ffffffff80770195>] early_idt_handler+0x55/0x69
> >  [<ffffffff8025be26>] ? getnstimeofday+0x46/0xc0
> >  [<ffffffff80258a81>] ktime_get_real+0x11/0x50
> >  [<ffffffff803aa8d1>] seed_std_data+0x11/0x30
> >  [<ffffffff8020ff60>] ? show_trace+0x10/0x20
> >  [<ffffffff803aa900>] seed_random_pools+0x10/0x30
> >  [<ffffffff8023dda9>] init_oops_id+0x9/0x40
> >  [<ffffffff8023dde9>] print_oops_end_marker+0x9/0x20
> >  [<ffffffff8023dfed>] warn_slowpath+0x9d/0xd0
> >  [<ffffffff802595e4>] ? up+0x34/0x50
> >  [<ffffffff8023e77d>] ? release_console_sem+0x1bd/0x210
> >  [<ffffffff80592c38>] ? printk+0x3c/0x44
> >  [<ffffffff80776e67>] mtrr_trim_uncached_memory+0x166/0x390
> >  [<ffffffff8077fca0>] ? early_gart_iommu_check+0xaf/0x2a7
> >  [<ffffffff80772574>] setup_arch+0x3ec/0x6a8
> >  [<ffffffff80770adf>] start_kernel+0x65/0x3c6
> >  [<ffffffff8077027d>] x86_64_start_reservations+0x7d/0x89
> >  [<ffffffff80770384>] x86_64_start_kernel+0xd8/0xdf
> > RIP 0x10
> > 
> > The clock is still null in kernel/time/timekeeping.c.
> > 
> > This one is to blame:
> > random-add-a-way-to-get-some-random-bits-into-the-entropy-pools-early-on.patch
> 
> urgh, OK, thanks, I'll drop it.
> 
> Presumably your machine picked a different clocksource from Arjan's,
> mine and others.  Now, how do we work out what clocksource you're
> using?
> 
> dmesg -s 1000000 | grep -i clock
> nope
> dmesg -s 1000000 | grep -i using
> nope

If we oops or warn while picking a timesource, we'll have lots of fun?

-- 
Mathematics is the supreme nostalgia of our time.

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