linux-kernel - Re: -git: BUG: unable to handle kernel paging request at c0100248 [CPU hotplug]

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Message-ID: <19f34abd0807271019i2112498ay57c267354bd63a8c@mail.gmail.com>
Date:	Sun, 27 Jul 2008 19:19:21 +0200
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	"Thomas Meyer" <thomas@...3r.de>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: -git: BUG: unable to handle kernel paging request at c0100248 [CPU hotplug]

On Sun, Jul 27, 2008 at 7:14 PM, Dmitry Adamushko
<dmitry.adamushko@...il.com> wrote:
> 2008/7/27 Vegard Nossum <vegard.nossum@...il.com>:
>> Hi,
>>
>> Something broke CPU-hotplug _again_, here with a freshly built latest -git:
>>
>> BUG: unable to handle kernel paging request at c0100248
>> IP: [<c067c3db>] native_cpu_up+0x26b/0x880
>> *pde = 00cc9067 *pte = 00100161
>> Oops: 0003 [#1] PREEMPT SMP DEBUG_PAGEALLOC
>> Pid: 3849, comm: bash Not tainted (2.6.26-07588-g5d1201a #5)
>> EIP: 0060:[<c067c3db>] EFLAGS: 00210282 CPU: 0
>> EIP is at native_cpu_up+0x26b/0x880
>> EAX: c08f9000 EBX: c08fa028 ECX: 01669000 EDX: c08f7004
>> ESI: 00000001 EDI: 00000000 EBP: f5bd9ed8 ESP: f5bd9dfc
>>  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
>> Process bash (pid: 3849, ti=f5bd8000 task=f480bfc0 task.ti=f5bd8000)
>> Stack: 00000000 c01e2153 f5bd9e3c f5992bb0 00000001 00000001 c01e2193 f5bd9e30
>>       c01e2223 f59929a0 f5bd9e3c f5992bb0 00000000 00000000 dead4ead ffffffff
>>       ffffffff c0889bc0 ffffffe0 f5bd9eec f5bd9ec4 f5bd9ea8 00000000 f5bd9e88
>> Call Trace:
>>  [<c01e2153>] ? __sysfs_add_one+0x63/0x90
>>  [<c01e2193>] ? sysfs_add_one+0x13/0x50
>>  [<c01e2223>] ? sysfs_addrm_start+0x53/0xa0
>>  [<c01e3811>] ? internal_create_group+0xd1/0x180
>>  [<c067bdc0>] ? do_fork_idle+0x0/0x20
>>  [<c014db69>] ? __raw_notifier_call_chain+0x19/0x20
>>  [<c067dbc3>] ? _cpu_up+0x83/0x100
>>  [<c067dc89>] ? cpu_up+0x49/0x80
>>  [<c065eb58>] ? store_online+0x58/0x80
>>  [<c065eb00>] ? store_online+0x0/0x80
>>  [<c03f443c>] ? sysdev_store+0x2c/0x40
>>  [<c01e16d2>] ? sysfs_write_file+0xa2/0x100
>>  [<c01a35a6>] ? vfs_write+0x96/0x130
>>  [<c01e1630>] ? sysfs_write_file+0x0/0x100
>>  [<c01a3aed>] ? sys_write+0x3d/0x70
>>  [<c0103f5b>] ? sysenter_do_call+0x12/0x3f
>>  =======================
>> Code: 34 ff ff ff b8 00 70 8f c0 03 04 95 80 8e 89 c0 8b 55 a8 89 10 8b 85 34 ff
>>  ff ff e8 f0 0a 00 00 8b b5 34 ff ff ff b8 00 90 8f c0 <c7> 05 48 02 10 c0 f0 c9
>>  67 c0 03 04 b5 80 8e 89 c0 a3 2e 31 81
>>
>> c067c3db:       c7 05 48 02 10 c0 f0    movl   $0xc067c9f0,0xc0100248
>> c067c3e2:       c9 67 c0
>>
>> $ addr2line -e vmlinux -i c067c3db
>> arch/x86/kernel/smpboot.c:859
>> arch/x86/kernel/smpboot.c:993
>>
>> Hm... that doesn't really make sense, does it? It's this line:
>>
>>        initial_code = (unsigned long)start_secondary;
>>
>> ..but I don't see where the memory dereference comes from.
>>
>>
>> I can reproduce it every time, simply by bringing CPU 1 down and up.
>
> cpu_up() is also executed during an initial boot-up of your system
> (for non boot-up cpus).
> You should see it with "dmesg | grep "Booting processor".
>
> So it has not caused any problems at that time... maybe something to
> do with __initdata.
> [ I'm a bit short of time so just speculating here :-) ]

Booting processor 1/1 ip 6000
Initializing CPU#1
[...]
Write protecting the kernel text: 5648k

So it succeeds because the protection happens much later :-)


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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