Re: mm: migrate_pages hang

[Sasha Levin]

On Sat, Mar 31, 2012 at 12:35 AM, Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Sat, 31 Mar 2012 00:23:30 +0200
> Sasha Levin <levinsasha928@xxxxxxxxx> wrote:
>
>> Hi all,
>>
>> I saw the following inside a KVM guest, this is the first time I
>> observed this hang and it seems to have started with today's
>> (20120330) -next.
>>
>> [ 3122.093136] INFO: task trinity:17328 blocked for more than 120 seconds.
>> [ 3122.093807] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
>> disables this message.
>> [ 3122.095237] trinity         D ffff8800703284d8  5648 17328   3101 0x00000004
>> [ 3122.096543]  ffff8800064cfb08 0000000000000082 ffff8800064cfab8
>> ffffffff8107d346
>> [ 3122.098087]  ffff8800064cffd8 00000000001d4580 ffff8800064ce010
>> 00000000001d4580
>> [ 3122.099447]  00000000001d4580 00000000001d4580 ffff8800064cffd8
>> 00000000001d4580
>> [ 3122.100607] Call Trace:
>> [ 3122.100983]  [<ffffffff8107d346>] ? kvm_clock_read+0x46/0x80
>> [ 3122.101950]  [<ffffffff81176260>] ? __lock_page+0x70/0x70
>> [ 3122.102761]  [<ffffffff827063d4>] schedule+0x24/0x70
>> [ 3122.103576]  [<ffffffff827064a7>] io_schedule+0x87/0xd0
>> [ 3122.104371]  [<ffffffff81176269>] sleep_on_page+0x9/0x10
>> [ 3122.105179]  [<ffffffff82704152>] __wait_on_bit_lock+0x52/0xb0
>> [ 3122.106042]  [<ffffffff81176252>] __lock_page+0x62/0x70
>> [ 3122.106811]  [<ffffffff810d78f0>] ? autoremove_wake_function+0x40/0x40
>> [ 3122.107450]  [<ffffffff811cc2f9>] lock_page+0x39/0x40
>> [ 3122.107976]  [<ffffffff811cd294>] __unmap_and_move+0x274/0x280
>> [ 3122.108848]  [<ffffffff81899061>] ? list_del+0x11/0x40
>> [ 3122.109385]  [<ffffffff811cd32d>] unmap_and_move+0x8d/0x130
>> [ 3122.109957]  [<ffffffff811cd47b>] migrate_pages+0xab/0x150
>> [ 3122.110788]  [<ffffffff811bc440>] ? isolate_freepages+0x390/0x390
>> [ 3122.111399]  [<ffffffff811bcc51>] compact_zone+0x1e1/0x2a0
>> [ 3122.111935]  [<ffffffff82707e15>] ? _raw_spin_unlock_irqrestore+0x75/0xa0
>> [ 3122.112579]  [<ffffffff811bcec3>] __compact_pgdat+0x1b3/0x200
>> [ 3122.113199]  [<ffffffff811bcf47>] compact_node+0x37/0x40
>> [ 3122.113631]  [<ffffffff81185080>] ? lru_add_drain_all+0x10/0x20
>> [ 3122.114266]  [<ffffffff811bcf98>] sysfs_compact_node+0x48/0x60
>> [ 3122.114768]  [<ffffffff8125c3d2>] ? sysfs_write_file+0x82/0xf0
>> [ 3122.115368]  [<ffffffff81b0dc3b>] dev_attr_store+0x1b/0x20
>> [ 3122.115877]  [<ffffffff8125c3ee>] sysfs_write_file+0x9e/0xf0
>> [ 3122.116423]  [<ffffffff811e3258>] vfs_write+0xc8/0x190
>> [ 3122.116934]  [<ffffffff811e340f>] sys_write+0x4f/0x90
>> [ 3122.117697]  [<ffffffff82708cf9>] system_call_fastpath+0x16/0x1b
>> [ 3122.118354] 2 locks held by trinity/17328:
>> [ 3122.118694]  #0:  (&buffer->mutex){+.+.+.}, at:
>> [<ffffffff8125c394>] sysfs_write_file+0x44/0xf0
>> [ 3122.119498]  #1:  (s_active#57){.+.+.+}, at: [<ffffffff8125c3d2>]
>> sysfs_write_file+0x82/0xf0
>
> You reported what I suppose is the same bug a week ago ("mm: hung task
> (handle_pte_fault)"): the kernel is waiting for a page to come
> unlocked, thinking that there is I/O outstanding against it.
>
> And my ugh still applies: "There are quite a lot of things which could
> cause this, alas.  VM, readahead, scheduler, core wait/wakeup code, IO
> system, interrupt system (if it happens outside KVM, I guess).  So....
> ugh.  Hopefully someone will hit this in a situation where it can be
> narrowed down or bisected."

Oh, I didn't think that this one was related to the one I've
previously reported.
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