latest -git: kernel BUG at arch/x86/kernel/microcode.c:142!

[Vegard Nossum]

Hi,

I just got this when doing CPU hotplug:

------------[ cut here ]------------
kernel BUG at arch/x86/kernel/microcode.c:142!
invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC

Pid: 4140, comm: bash Not tainted (2.6.26-06371-g338b9bb-dirty #14)
EIP: 0060:[<c0117f1e>] EFLAGS: 00210202 CPU: 0
EIP is at __mc_sysdev_add+0x1ee/0x200
EAX: 00000000 EBX: c1f61028 ECX: 01798000 EDX: c081ac80
ESI: 00000001 EDI: 00000001 EBP: f5bcbe24 ESP: f5bcbdcc
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process bash (pid: 4140, ti=f5bca000 task=f4066f90 task.ti=f5bca000)
Stack: 00000000 f5bcbe24 c028300b 00000001 000000d0 c06d8dc3 f73f77d0 00000000
       00000000 00000014 00000000 00000000 c0829254 f4f0fa00 f6e950f0 00200282
       f6d5180c 00000002 00000003 00000002 00000001 c1f61028 f5bcbe2c c0117f3a
Call Trace:
 [<c028300b>] ? kobject_uevent_env+0xdb/0x380
 [<c0117f3a>] ? mc_sysdev_add+0xa/0x10
 [<c05875fa>] ? mc_cpu_callback+0x1ea/0x240
 [<c014db67>] ? notifier_call_chain+0x37/0x70
 [<c014dbd9>] ? __raw_notifier_call_chain+0x19/0x20
 [<c014dbfa>] ? raw_notifier_call_chain+0x1a/0x20
 [<c0589477>] ? _cpu_up+0xa7/0x100
 [<c0589519>] ? cpu_up+0x49/0x80
 [<c056a3d8>] ? store_online+0x58/0x80
 [<c056a380>] ? store_online+0x0/0x80
 [<c02ff57c>] ? sysdev_store+0x2c/0x40
 [<c01de412>] ? sysfs_write_file+0xa2/0x100
 [<c01a0386>] ? vfs_write+0x96/0x130
 [<c01de370>] ? sysfs_write_file+0x0/0x100
 [<c01a08cd>] ? sys_write+0x3d/0x70
 [<c0103f5b>] ? sysenter_do_call+0x12/0x3f
 =======================
Code: 4d d8 c7 01 00 00 00 00 b8 00 1a 6f c0 e8 fb 46 47 00 8d 55 f0
64 a1 00 90 7c c0 e8 0d 75 01 00 8b 45 d4 83 c4 4c 5b 5e 5f 5d c3 <0f>
0b eb fe 8d b4 26 00 00 00 00 8d bc 27 00 00 00 00 55 31 d2
EIP: [<c0117f1e>] __mc_sysdev_add+0x1ee/0x200 SS:ESP 0068:f5bcbdcc
---[ end trace 8c86c730d90bf362 ]---

It's this one:

        /* We should bind the task to the CPU */
        BUG_ON(raw_smp_processor_id() != cpu_num);

Maybe related to recently merged per-cpu changes? (Yesterday's tests ran fine.)

It seems 100% reproducible, so I'll start bisecting it.


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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