kernel BUG at kernel/smpboot.c:134!

[Dave Hansen <dave@sr71.net>]

Hey Thomas,

I seem to be running in to smpboot_thread_fn()'s

	BUG_ON(td->cpu != smp_processor_id());

pretty regularly, both at boot and if I boot with maxcpus=x and then
online the CPUs from sysfs after boot.  It's a 160-logical-cpu system,
so it's quite a beast.  I _seem_ to be hitting it more often at higher
cpu counts, but it doesn't trigger on bringing up a particular CPU as
far as I can tell.

This is on a pull of mainline from today, e0a77f263.  Any ideas?

> [  790.223270] ------------[ cut here ]------------
> [  790.223966] kernel BUG at kernel/smpboot.c:134!
> [  790.224739] invalid opcode: 0000 [#1] SMP 
> [  790.225671] Modules linked in:
> [  790.226428] CPU 81 
> [  790.226909] Pid: 3909, comm: migration/135 Tainted: G        W    3.9.0-rc5-00184-gb6a9b7f-dirty #118 FUJITSU-SV PRIMEQUEST 1800E2/SB
> [  790.228775] RIP: 0010:[<ffffffff8110bee8>]  [<ffffffff8110bee8>] smpboot_thread_fn+0x258/0x280
> [  790.230205] RSP: 0018:ffff88bfef9c1e08  EFLAGS: 00010202
> [  790.231090] RAX: 0000000000000051 RBX: ffff88bfefb82000 RCX: 000000000000b888
> [  790.231653] RDX: ffff88bfef9c1fd8 RSI: ffff881fff000000 RDI: 0000000000000087
> [  790.232085] RBP: ffff88bfef9c1e38 R08: 0000000000000001 R09: 0000000000000000
> [  790.232850] R10: 0000000000000018 R11: 0000000000000000 R12: ffff88bfec9e22e0
> [  790.233561] R13: ffffffff81e587a0 R14: ffff88bfec9e22e0 R15: 0000000000000000
> [  790.234004] FS:  0000000000000000(0000) GS:ffff881fff000000(0000) knlGS:0000000000000000
> [  790.234918] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [  790.235602] CR2: 00007fa89a333c62 CR3: 0000000001e0b000 CR4: 00000000000007e0
> [  790.236110] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [  790.236584] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> [  790.237329] Process migration/135 (pid: 3909, threadinfo ffff88bfef9c0000, task ffff88bfec9e22e0)
> [  790.238321] Stack:
> [  790.238882]  ffff88bfef9c1e38 0000000000000000 ffff88ffef421cc0 ffff88bfef9c1ec0
> [  790.245415]  ffff88bfefb82000 ffffffff8110bc90 ffff88bfef9c1f48 ffffffff810ff1df
> [  790.250755]  0000000000000001 0000000000000087 ffff88bfefb82000 0000000000000000
> [  790.253365] Call Trace:
> [  790.254121]  [<ffffffff8110bc90>] ? __smpboot_create_thread+0x180/0x180
> [  790.255428]  [<ffffffff810ff1df>] kthread+0xef/0x100
> [  790.256071]  [<ffffffff819cb1a4>] ? wait_for_completion+0x124/0x180
> [  790.256697]  [<ffffffff810ff0f0>] ? __init_kthread_worker+0x80/0x80
> [  790.257325]  [<ffffffff819dba9c>] ret_from_fork+0x7c/0xb0
> [  790.258233]  [<ffffffff810ff0f0>] ? __init_kthread_worker+0x80/0x80
> [  790.258942] Code: ef 3d 01 01 48 89 df e8 87 b0 16 00 48 83 05 67 ef 3d 01 01 48 83 c4 10 31 c0 5b 41 5c 41 5d 41 5e 5d c3 48 83 05 90 ef 3d 01 01 <0f> 0b 48 83 05 96 ef 3d 01 01 48 83 05 56 ef 3d 01 01 0f 0b 48 
> [  790.276178] RIP  [<ffffffff8110bee8>] smpboot_thread_fn+0x258/0x280
> [  790.276735]  RSP <ffff88bfef9c1e08>
> [  790.278348] ---[ end trace 84baa2bee1434240 ]---