Stack from kworker:
[ 240.608612] INFO: task kworker/0:2:861 blocked for more than 120 seconds.
[ 240.608617] Not tainted 3.13.0-17-generic #37-Ubuntu
[ 240.608618] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[ 240.608620] kworker/0:2 D ffff88001e414440 0 861 2
0x00000000
[ 240.608628] Workqueue: events hot_add_req [hv_balloon]
[ 240.608630] ffff88001a00fb30 0000000000000002 ffff88001a6f8000
ffff88001a00ffd8
[ 240.608632] 0000000000014440 0000000000014440 ffff88001a6f8000
ffff88001aac6c98
[ 240.608635] ffff88001aac6c9c ffff88001a6f8000 00000000ffffffff
ffff88001aac6ca0
[ 240.608637] Call Trace:
[ 240.608643] [<ffffffff817159f9>] schedule_preempt_disabled+0x29/0x70
[ 240.608645] [<ffffffff81717865>] __mutex_lock_slowpath+0x135/0x1b0
[ 240.608647] [<ffffffff817178ff>] mutex_lock+0x1f/0x2f
[ 240.608651] [<ffffffff8148a5bd>] device_attach+0x1d/0xa0
[ 240.608653] [<ffffffff81489a38>] bus_probe_device+0x98/0xc0
[ 240.608656] [<ffffffff81487895>] device_add+0x4c5/0x640
[ 240.608658] [<ffffffff81487a2a>] device_register+0x1a/0x20
[ 240.608661] [<ffffffff8149e000>] init_memory_block+0xd0/0xf0
[ 240.608663] [<ffffffff8149e141>] register_new_memory+0x91/0xa0
[ 240.608666] [<ffffffff81700d10>] __add_pages+0x140/0x240
[ 240.608670] [<ffffffff81055649>] arch_add_memory+0x59/0xd0
[ 240.608672] [<ffffffff81700fe4>] add_memory+0xe4/0x1f0
[ 240.608675] [<ffffffffa00411cf>] hot_add_req+0x31f/0x1150 [hv_balloon]
[ 240.608679] [<ffffffff810824a2>] process_one_work+0x182/0x450
[ 240.608681] [<ffffffff81083241>] worker_thread+0x121/0x410
[ 240.608683] [<ffffffff81083120>] ? rescuer_thread+0x3e0/0x3e0
[ 240.608686] [<ffffffff81089ed2>] kthread+0xd2/0xf0
[ 240.608688] [<ffffffff81089e00>] ? kthread_create_on_node+0x190/0x190
[ 240.608691] [<ffffffff817219bc>] ret_from_fork+0x7c/0xb0
[ 240.608693] [<ffffffff81089e00>] ? kthread_create_on_node+0x190/0x190
kworker looks to be blocked on the device lock in device_attach:
int device_attach(struct device *dev)
{
int ret = 0;
device_lock(dev);
[...]
}
If we follow the call trace we take mem_hotplug_mutex in add_memory():
int __ref add_memory(int nid, u64 start, u64 size)
{
[...]
lock_memory_hotplug();
}
We later call device_add which triggers the udev event for this block:
int device_add(struct device *dev)
{
kobject_uevent(&dev->kobj, KOBJ_ADD);
[...]
}
Finally, after emitting this event and and while holding that we call
device_attach() above, nesting the device_lock(dev) inside the memory
hotplug lock.
Stack from systemd-udevd:
[ 240.608705] INFO: task systemd-udevd:1906 blocked for more than 120
seconds.
[ 240.608706] Not tainted 3.13.0-17-generic #37-Ubuntu
[ 240.608707] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[ 240.608708] systemd-udevd D ffff88001e414440 0 1906 404
0x00000004
[ 240.608710] ffff88001a97bd20 0000000000000002 ffff8800170e0000
ffff88001a97bfd8
[ 240.608712] 0000000000014440 0000000000014440 ffff8800170e0000
ffffffff81c620e0
[ 240.608714] ffffffff81c620e4 ffff8800170e0000 00000000ffffffff
ffffffff81c620e8
[ 240.608716] Call Trace:
[ 240.608719] [<ffffffff817159f9>] schedule_preempt_disabled+0x29/0x70
[ 240.608721] [<ffffffff81717865>] __mutex_lock_slowpath+0x135/0x1b0
[ 240.608725] [<ffffffff8115a8ae>] ? lru_cache_add+0xe/0x10
[ 240.608727] [<ffffffff817178ff>] mutex_lock+0x1f/0x2f
[ 240.608729] [<ffffffff817019c3>] online_pages+0x33/0x570
[ 240.608731] [<ffffffff8149dd98>] memory_subsys_online+0x68/0xd0
[ 240.608733] [<ffffffff814881e5>] device_online+0x65/0x90
[ 240.608735] [<ffffffff8149da24>] store_mem_state+0x64/0x160
[ 240.608738] [<ffffffff81485748>] dev_attr_store+0x18/0x30
[ 240.608742] [<ffffffff8122e698>] sysfs_write_file+0x128/0x1c0
[ 240.608745] [<ffffffff811b88c4>] vfs_write+0xb4/0x1f0
[ 240.608747] [<ffffffff811b92f9>] SyS_write+0x49/0xa0
[ 240.608749] [<ffffffff81721c7f>] tracesys+0xe1/0xe6
udevd seems to be blocked on the hotplug lock:
int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int
online_type)
{
[...]
lock_memory_hotplug();
[...]
mutex_lock(&zonelists_mutex);
[...]
}
Note that udevd would have taken the device lock in device_online():
int device_online(struct device *dev)
{
int ret = 0;
device_lock(dev);
[...]
}
And while holding this we call online_pages() as above, nesting the memory
hotplug lock inside the device_lock(dev).
This looks to be an ABBA deadlock, assuming dev is the same in these two
cases which seems plausible as we emit the udev event in the middle.
--
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Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1292400
Title:
task systemd-udevd:1906 blocked for more than 120 seconds.
Status in “linux” package in Ubuntu:
Confirmed
Bug description:
System log shows repeated incidents of "task systemd-udevd:1906
blocked for more than 120 seconds."
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: linux-image-3.13.0-17-generic 3.13.0-17.37 [modified:
boot/vmlinuz-3.13.0-17-generic]
ProcVersionSignature: Ubuntu 3.13.0-17.37-generic 3.13.6
Uname: Linux 3.13.0-17-generic x86_64
ApportVersion: 2.13.3-0ubuntu1
Architecture: amd64
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
'/dev/snd/timer'] failed with exit code 1:
CurrentDesktop: XFCE
Date: Fri Mar 14 08:54:36 2014
HibernationDevice: RESUME=UUID=0d223c65-8c7e-41b4-95b3-05b22ff4679b
InstallationDate: Installed on 2014-03-12 (1 days ago)
InstallationMedia: Xubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140312)
IwConfig:
eth0 no wireless extensions.
lo no wireless extensions.
Lspci:
Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize
libusb: -99
MachineType: Microsoft Corporation Virtual Machine
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-17-generic.efi.signed
root=UUID=61b52c1b-300d-4c30-8966-db1745f4a4bc ro video:hyperv_fb=1920x1080
quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-3.13.0-17-generic N/A
linux-backports-modules-3.13.0-17-generic N/A
linux-firmware 1.126
RfKill:
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/26/2012
dmi.bios.vendor: Microsoft Corporation
dmi.bios.version: Hyper-V UEFI Release v1.0
dmi.board.asset.tag: None
dmi.board.name: Virtual Machine
dmi.board.vendor: Microsoft Corporation
dmi.board.version: Hyper-V UEFI Release v1.0
dmi.chassis.asset.tag: 6485-6574-9248-6162-4701-6267-50
dmi.chassis.type: 3
dmi.chassis.vendor: Microsoft Corporation
dmi.chassis.version: Hyper-V UEFI Release v1.0
dmi.modalias:
dmi:bvnMicrosoftCorporation:bvrHyper-VUEFIReleasev1.0:bd11/26/2012:svnMicrosoftCorporation:pnVirtualMachine:pvrHyper-VUEFIReleasev1.0:rvnMicrosoftCorporation:rnVirtualMachine:rvrHyper-VUEFIReleasev1.0:cvnMicrosoftCorporation:ct3:cvrHyper-VUEFIReleasev1.0:
dmi.product.name: Virtual Machine
dmi.product.version: Hyper-V UEFI Release v1.0
dmi.sys.vendor: Microsoft Corporation
---
ApportVersion: 2.13.3-0ubuntu1
Architecture: amd64
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
'/dev/snd/timer'] failed with exit code 1:
CurrentDesktop: XFCE
DistroRelease: Ubuntu 14.04
HibernationDevice: RESUME=UUID=0d223c65-8c7e-41b4-95b3-05b22ff4679b
InstallationDate: Installed on 2014-03-12 (1 days ago)
InstallationMedia: Xubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140312)
IwConfig:
eth0 no wireless extensions.
lo no wireless extensions.
Lspci:
Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize
libusb: -99
MachineType: Microsoft Corporation Virtual Machine
Package: linux (not installed)
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-17-generic.efi.signed
root=UUID=61b52c1b-300d-4c30-8966-db1745f4a4bc ro video:hyperv_fb=1920x1080
quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 3.13.0-17.37-generic 3.13.6
RelatedPackageVersions:
linux-restricted-modules-3.13.0-17-generic N/A
linux-backports-modules-3.13.0-17-generic N/A
linux-firmware 1.126
RfKill:
Tags: trusty
Uname: Linux 3.13.0-17-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
_MarkForUpload: True
dmi.bios.date: 11/26/2012
dmi.bios.vendor: Microsoft Corporation
dmi.bios.version: Hyper-V UEFI Release v1.0
dmi.board.asset.tag: None
dmi.board.name: Virtual Machine
dmi.board.vendor: Microsoft Corporation
dmi.board.version: Hyper-V UEFI Release v1.0
dmi.chassis.asset.tag: 6485-6574-9248-6162-4701-6267-50
dmi.chassis.type: 3
dmi.chassis.vendor: Microsoft Corporation
dmi.chassis.version: Hyper-V UEFI Release v1.0
dmi.modalias:
dmi:bvnMicrosoftCorporation:bvrHyper-VUEFIReleasev1.0:bd11/26/2012:svnMicrosoftCorporation:pnVirtualMachine:pvrHyper-VUEFIReleasev1.0:rvnMicrosoftCorporation:rnVirtualMachine:rvrHyper-VUEFIReleasev1.0:cvnMicrosoftCorporation:ct3:cvrHyper-VUEFIReleasev1.0:
dmi.product.name: Virtual Machine
dmi.product.version: Hyper-V UEFI Release v1.0
dmi.sys.vendor: Microsoft Corporation
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