kernel-packages team mailing list archive

Thread
Date
[Bug 928895] Re: filesystem deadlock sshfs precise kernel 3.2.0-12-generic

To: kernel-packages@xxxxxxxxxxxxxxxxxxx
From: "Christopher M. Penalver" <christopher.m.penalver@xxxxxxxxx>
Date: Tue, 20 Aug 2013 09:50:14 -0000
Reply-to: Bug 928895 <928895@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx
ray, could you please confirm this issue exists with the latest
development release of Ubuntu? ISO images are available from
http://cdimage.ubuntu.com/daily-live/current/ . If the issue remains,
could you please run the following command in the development release
from a Terminal (Applications->Accessories->Terminal), as it will
automatically gather and attach updated debug information to this
report:

apport-collect -p linux <replace-with-bug-number>

Also, could you please test the latest upstream kernel available following https://wiki.ubuntu.com/KernelMainlineBuilds ? It will allow additional upstream developers to examine the issue. Please do not test the daily folder, but the one all the way at the bottom. Once you've tested the upstream kernel, please comment on which kernel version specifically you tested. If this bug is fixed in the mainline kernel, please add the following tags:
kernel-fixed-upstream
kernel-fixed-upstream-VERSION-NUMBER

where VERSION-NUMBER is the version number of the kernel you tested. For example:
kernel-fixed-upstream-v3.11-rc5

This can be done by clicking on the yellow circle with a black pencil icon next to the word Tags located at the bottom of the bug description. As well, please remove the tag:
needs-upstream-testing

If the mainline kernel does not fix this bug, please add the following tags:
kernel-bug-exists-upstream
kernel-bug-exists-upstream-VERSION-NUMBER

As well, please remove the tag:
needs-upstream-testing

Once testing of the upstream kernel is complete, please mark this bug's
Status as Confirmed. Please let us know your results. Thank you for your
understanding.

** Tags added: needs-kernel-logs needs-upstream-testing

** Changed in: linux (Ubuntu)
       Status: Confirmed => Incomplete

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/928895

Title:
  filesystem deadlock sshfs precise kernel 3.2.0-12-generic

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  On precise i was rsyncing files over a sshfs mountpoint. The transfer
  itself is extremely slow in overall but that does not indicate a bug
  itself. But while the transfer was running i started browsing files
  with the filemanager also over the mountpoint and now it froze the
  rsync file transfer and the filemanager (Thunar to be specific). Rsync
  and Thunar are frozen and don't respond to signals. It's a multicore
  64 bit system. Here you have the uname, lsb_release and the output
  dmesg shows.

  uname -a
  Linux hostname 3.2.0-12-generic #21-Ubuntu SMP Tue Jan 31 18:48:57 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

  lsb_release -a
  No LSB modules are available.
  Distributor ID:	Ubuntu
  Description:	Ubuntu precise (development branch)
  Release:	12.04
  Codename:	precise

  [181784.220336] INFO: task pool:2826 blocked for more than 120 seconds.
  [181784.220344] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.220350] pool            D ffffffff81806240     0  2826      1 0x00000000
  [181784.220361]  ffff8800d9d6fbb8 0000000000000086 ffff88020a8d9001 ffff8800d9d6fca0
  [181784.220373]  ffff8800d9d6ffd8 ffff8800d9d6ffd8 ffff8800d9d6ffd8 0000000000013780
  [181784.220382]  ffff8802102516e0 ffff880037ac8000 ffff8800d9d6fbd8 ffff8800d39e4360
  [181784.220392] Call Trace:
  [181784.220410]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.220419]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.220428]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.220437]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.220445]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.220456]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.220464]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.220471]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.220481]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.220492]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.220501]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.220508]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.220515]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.220523]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.220531]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.220542]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.220549] INFO: task pool:2842 blocked for more than 120 seconds.
  [181784.220553] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.220557] pool            D ffffffff81806240     0  2842      1 0x00000000
  [181784.220566]  ffff880088a45bb8 0000000000000086 ffff880003005001 ffff880088a45ca0
  [181784.220575]  ffff880088a45fd8 ffff880088a45fd8 ffff880088a45fd8 0000000000013780
  [181784.220584]  ffffffff81c0d020 ffff880112f85b80 ffff880088a45bd8 ffff8800d39e4360
  [181784.220593] Call Trace:
  [181784.220601]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.220609]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.220616]  [<ffffffff81182264>] ? path_get+0x44/0x50
  [181784.220624]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.220630]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.220638]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.220647]  [<ffffffff8119375e>] ? vfsmount_lock_local_unlock+0x1e/0x30
  [181784.220656]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.220663]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.220670]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.220678]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.220687]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.220695]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.220701]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.220709]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.220716]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.220724]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.220734]  [<ffffffff810146b5>] ? math_state_restore+0x45/0x60
  [181784.220741]  [<ffffffff8165457e>] ? do_device_not_available+0xe/0x10
  [181784.220749]  [<ffffffff8165db0b>] ? device_not_available+0x1b/0x20
  [181784.220758]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.220764] INFO: task pool:2844 blocked for more than 120 seconds.
  [181784.220768] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.220772] pool            D ffffffff81806240     0  2844      1 0x00000000
  [181784.220780]  ffff88003797fbb8 0000000000000086 ffff8801ed9c5001 ffff88003797fca0
  [181784.220789]  ffff88003797ffd8 ffff88003797ffd8 ffff88003797ffd8 0000000000013780
  [181784.220797]  ffff8802102796e0 ffff880112f844a0 ffff88003797fbd8 ffff8800d39e4360
  [181784.220806] Call Trace:
  [181784.220814]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.220822]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.220830]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.220837]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.220844]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.220851]  [<ffffffff8119375e>] ? vfsmount_lock_local_unlock+0x1e/0x30
  [181784.220860]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.220867]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.220874]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.220882]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.220890]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.220898]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.220905]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.220912]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.220920]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.220927]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.220935]  [<ffffffff810146b5>] ? math_state_restore+0x45/0x60
  [181784.220942]  [<ffffffff8165457e>] ? do_device_not_available+0xe/0x10
  [181784.220949]  [<ffffffff8165db0b>] ? device_not_available+0x1b/0x20
  [181784.220957]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.220963] INFO: task pool:2846 blocked for more than 120 seconds.
  [181784.220967] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.220971] pool            D ffffffff81806240     0  2846      1 0x00000000
  [181784.220979]  ffff88005a287bb8 0000000000000086 ffff880058f22001 ffff88005a287ca0
  [181784.220988]  ffff88005a287fd8 ffff88005a287fd8 ffff88005a287fd8 0000000000013780
  [181784.220997]  ffff8802101c96e0 ffff8801499396e0 ffff88005a287bd8 ffff8800d39e4360
  [181784.221005] Call Trace:
  [181784.221013]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.221020]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.221029]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.221035]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.221042]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.221049]  [<ffffffff8119375e>] ? vfsmount_lock_local_unlock+0x1e/0x30
  [181784.221058]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.221065]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.221072]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.221080]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.221088]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.221096]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.221103]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.221111]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.221118]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.221125]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.221134]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.221140] INFO: task pool:2848 blocked for more than 120 seconds.
  [181784.221144] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.221148] pool            D 0000000000000004     0  2848      1 0x00000000
  [181784.221156]  ffff8800373a3bb8 0000000000000086 ffff8800d9702001 ffff8800373a3ca0
  [181784.221165]  ffff8800373a3fd8 ffff8800373a3fd8 ffff8800373a3fd8 0000000000013780
  [181784.221174]  ffff8800dafdadc0 ffff88014993adc0 ffff8800373a3bd8 ffff8800d39e4360
  [181784.221182] Call Trace:
  [181784.221190]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.221197]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.221204]  [<ffffffff81182264>] ? path_get+0x44/0x50
  [181784.221212]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.221218]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.221225]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.221232]  [<ffffffff8119375e>] ? vfsmount_lock_local_unlock+0x1e/0x30
  [181784.221241]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.221248]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.221255]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.221263]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.221271]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.221279]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.221286]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.221293]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.221300]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.221308]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.221317]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.221322] INFO: task pool:2849 blocked for more than 120 seconds.
  [181784.221326] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.221330] pool            D ffffffff81806240     0  2849      1 0x00000000
  [181784.221338]  ffff8800d383bbb8 0000000000000086 ffff88020a8dd001 ffff8800d383bca0
  [181784.221347]  ffff8800d383bfd8 ffff8800d383bfd8 ffff8800d383bfd8 0000000000013780
  [181784.221355]  ffff8802102516e0 ffff88014993db80 ffff8800d383bbd8 ffff8800d39e4360
  [181784.221364] Call Trace:
  [181784.221371]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.221379]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.221385]  [<ffffffff81182264>] ? path_get+0x44/0x50
  [181784.221393]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.221400]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.221407]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.221415]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.221422]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.221429]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.221437]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.221445]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.221453]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.221459]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.221467]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.221474]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.221481]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.221490]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.221496] INFO: task pool:2851 blocked for more than 120 seconds.
  [181784.221500] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.221504] pool            D 0000000000000002     0  2851      1 0x00000000
  [181784.221511]  ffff8800d9d4fbb8 0000000000000086 ffff8800ca25f001 ffff8800d9d4fca0
  [181784.221520]  ffff8800d9d4ffd8 ffff8800d9d4ffd8 ffff8800d9d4ffd8 0000000000013780
  [181784.221529]  ffff8801e0bc2dc0 ffff88021021db80 ffff8800d9d4fbd8 ffff8800d39e4360
  [181784.221538] Call Trace:
  [181784.221546]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.221554]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.221560]  [<ffffffff81182264>] ? path_get+0x44/0x50
  [181784.221568]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.221574]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.221581]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.221588]  [<ffffffff8119375e>] ? vfsmount_lock_local_unlock+0x1e/0x30
  [181784.221597]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.221604]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.221611]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.221618]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.221627]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.221634]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.221641]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.221648]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.221656]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.221663]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.221672]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181784.221678] INFO: task pool:2853 blocked for more than 120 seconds.
  [181784.221682] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181784.221686] pool            D ffffffff81806240     0  2853      1 0x00000000
  [181784.221693]  ffff8800daedfbb8 0000000000000086 ffff880058f25001 ffff8800daedfca0
  [181784.221702]  ffff8800daedffd8 ffff8800daedffd8 ffff8800daedffd8 0000000000013780
  [181784.221711]  ffff8802102516e0 ffff88020b88adc0 ffff8800daedfbd8 ffff8800d39e4360
  [181784.221720] Call Trace:
  [181784.221727]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181784.221735]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181784.221743]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181784.221750]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181784.221757]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181784.221765]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181784.221772]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181784.221779]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181784.221787]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181784.221795]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181784.221803]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181784.221810]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181784.221817]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181784.221824]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181784.221831]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181784.221841]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181903.971920] INFO: task pool:2826 blocked for more than 120 seconds.
  [181903.971927] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181903.971933] pool            D ffffffff81806240     0  2826      1 0x00000000
  [181903.971944]  ffff8800d9d6fbb8 0000000000000086 ffff88020a8d9001 ffff8800d9d6fca0
  [181903.971956]  ffff8800d9d6ffd8 ffff8800d9d6ffd8 ffff8800d9d6ffd8 0000000000013780
  [181903.971965]  ffff8802102516e0 ffff880037ac8000 ffff8800d9d6fbd8 ffff8800d39e4360
  [181903.971975] Call Trace:
  [181903.971992]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181903.972002]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181903.972011]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181903.972020]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181903.972027]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181903.972039]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181903.972046]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181903.972054]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181903.972064]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181903.972074]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181903.972083]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181903.972091]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181903.972098]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181903.972106]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181903.972114]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181903.972125]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b
  [181903.972132] INFO: task pool:2842 blocked for more than 120 seconds.
  [181903.972135] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  [181903.972140] pool            D ffffffff81806240     0  2842      1 0x00000000
  [181903.972149]  ffff880088a45bb8 0000000000000086 ffff880003005001 ffff880088a45ca0
  [181903.972158]  ffff880088a45fd8 ffff880088a45fd8 ffff880088a45fd8 0000000000013780
  [181903.972167]  ffffffff81c0d020 ffff880112f85b80 ffff880088a45bd8 ffff8800d39e4360
  [181903.972176] Call Trace:
  [181903.972183]  [<ffffffff8165162f>] schedule+0x3f/0x60
  [181903.972192]  [<ffffffff81652437>] __mutex_lock_slowpath+0xd7/0x150
  [181903.972199]  [<ffffffff81182264>] ? path_get+0x44/0x50
  [181903.972207]  [<ffffffff8165204a>] mutex_lock+0x2a/0x50
  [181903.972213]  [<ffffffff81182d46>] do_lookup+0x1d6/0x310
  [181903.972221]  [<ffffffff81184aac>] path_lookupat+0x11c/0x750
  [181903.972229]  [<ffffffff8119375e>] ? vfsmount_lock_local_unlock+0x1e/0x30
  [181903.972238]  [<ffffffff81314667>] ? __strncpy_from_user+0x27/0x60
  [181903.972245]  [<ffffffff81185111>] do_path_lookup+0x31/0xc0
  [181903.972252]  [<ffffffff81185c19>] user_path_at_empty+0x59/0xa0
  [181903.972260]  [<ffffffff812d3964>] ? apparmor_inode_getattr+0x54/0x60
  [181903.972269]  [<ffffffff8165353e>] ? _raw_spin_lock+0xe/0x20
  [181903.972277]  [<ffffffff8117ab08>] ? cp_new_stat+0xf8/0x110
  [181903.972284]  [<ffffffff81185c71>] user_path_at+0x11/0x20
  [181903.972291]  [<ffffffff8117ad2a>] vfs_fstatat+0x3a/0x70
  [181903.972299]  [<ffffffff8117ad7e>] vfs_lstat+0x1e/0x20
  [181903.972306]  [<ffffffff8117af1a>] sys_newlstat+0x1a/0x40
  [181903.972317]  [<ffffffff810146b5>] ? math_state_restore+0x45/0x60
  [181903.972324]  [<ffffffff8165457e>] ? do_device_not_available+0xe/0x10
  [181903.972332]  [<ffffffff8165db0b>] ? device_not_available+0x1b/0x20
  [181903.972341]  [<ffffffff8165bb02>] system_call_fastpath+0x16/0x1b

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/928895/+subscriptions