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Date: Sun, 14 Jun 2009 23:40:17 +0400
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Simon Holm =?iso-8859-1?Q?Th=F8gersen?= <odie@cs.aau.dk>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <andi@firstfloor.org>
Subject: Re: apic: native_apic_write_dummy warning
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[Cyrill Gorcunov - Sun, Jun 14, 2009 at 11:22:20PM +0400]
| [Simon Holm Th?gersen - Sun, Jun 14, 2009 at 09:05:50PM +0200]
| | Hi Cyrill
| | 
| | I guess you want to know about these warnings, so here you go
| | 
| | WARNING: at arch/x86/kernel/apic/apic.c:249 native_apic_write_dummy+0x32/0x3e()
| | Hardware name:
| | Modules linked in:
| | Pid: 0, comm: swapper Not tainted 2.6.30-debug-03392-g44b7532 #17
| | Call Trace:
| |  [<c0126bed>] warn_slowpath_common+0x65/0x95
| | [    0.006956]  [<c0126c2f>] warn_slowpath_null+0x12/0x15
| | [    0.007031]  [<c0112269>] native_apic_write_dummy+0x32/0x3e
| | [    0.007109]  [<c010e027>] intel_init_thermal+0xd3/0x178
| | [    0.007185]  [<c01168ce>] ? native_read_msr_safe+0x9/0x16
| | [    0.007263]  [<c0194197>] ? __kmalloc+0x117/0x123
| | [    0.007338]  [<c010deb2>] mce_intel_feature_init+0x10/0x50
| | [    0.007416]  [<c05ee0a4>] mcheck_init+0x1d5/0x263
| | [    0.007492]  [<c05eda0a>] identify_cpu+0x369/0x378
| | [    0.007569]  [<c03432ac>] ? _spin_unlock+0x3d/0x49
| | [    0.007644]  [<c01cc5ff>] ? proc_register+0x150/0x161
| | [    0.007721]  [<c05d2a15>] identify_boot_cpu+0xd/0x23
| | [    0.007796]  [<c05d2a67>] check_bugs+0xb/0xf1
| | [    0.007872]  [<c05cc966>] start_kernel+0x293/0x2a7
| | [    0.008011]  [<c05cc30b>] i386_start_kernel+0x65/0x6a
| | 
| | 
| | Simon Holm Th?gersen
| 
| Hi Simon, thanks a lot for report! Will take a look.
| 
| 	-- Cyrill

Neither thermal interrupts nor mce will be functional if apic
is not properly set up (even having kernel compiled that way
it support both). So you may try to pass "lapic" boot option
and check if we're lucky in attempt to enable apic via force
push. Anyway this warn show that the code is to be fixed
(and native_apic_write_dummy done its work great catching
 useless apic->write operation). I'll handle it but a bit later.

Andi CC'ed since he is involved in MCE handling just for the
record.

	-- Cyrill
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