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Date: Mon, 25 Aug 2008 23:37:29 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Ryan Hope" <rmh3093@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@elte.hu>,
       Mike Travis <travis@sgi.com>
Subject: Re: [-mmotm] BUG: scheduling while atomic: swapper
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On Mon, 25 Aug 2008 22:09:25 -0400 "Ryan Hope" <rmh3093@gmail.com> wrote:

> BUG: scheduling while atomic: swapper/1/0x00000002
> Modules linked in:
> Pid: 1, comm: swapper Tainted: G        W 2.6.27-rc4-zenmmotm1 #4
>  [<c057a0c7>] schedule+0x287/0x6d0
>  [<c03672e6>] vsnprintf+0x3a6/0x6c0
>  [<c057a92d>] schedule_timeout+0x7d/0xb0
>  [<c021e0c8>] __wake_up+0x38/0x50
>  [<c057a74a>] wait_for_common+0x8a/0x130
>  [<c0220ab0>] default_wake_function+0x0/0x10
>  [<c0237743>] call_usermodehelper_exec+0xc3/0xf0
>  [<c0362ede>] kobject_uevent_env+0x37e/0x3a0
>  [<c03d5921>] device_add+0x551/0x630
>  [<c03d5ac3>] device_create_vargs+0xb3/0xd0
>  [<c06ccc47>] microcode_intel_module_init+0x0/0x39
>  [<c03d5b0b>] device_create+0x2b/0x30
>  [<c0385f2e>] misc_register+0xbe/0x170
>  [<c02137d1>] microcode_init+0x21/0xf0
>  [<c0201336>] do_one_initcall+0x26/0x170
>  [<c021e0c8>] __wake_up+0x38/0x50
>  [<c0237c98>] insert_work+0x48/0x50
>  [<c02380a5>] __queue_work+0x25/0x40
>  [<c023812a>] queue_work_on+0x3a/0x50
>  [<c06c29bf>] kernel_init+0x170/0x251
>  [<c06c284f>] kernel_init+0x0/0x251
>  [<c0204157>] kernel_thread_helper+0x7/0x10
>  =======================

As a mad guess, I'd guess that someone changed get_online_cpus() so
that disables preemption (with a suitable config combination, perhaps).
Which would cause microcode_init()'s sysdev_driver_register() to run
in atomic context.

But that's just a guess - I can't immediately see any change in there
which does this.  Ingo, any theories?

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