** Package changed: linux-signed (Ubuntu) => linux (Ubuntu)
** Changed in: linux (Ubuntu)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu)
Status: New => Triaged
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Bionic)
Importance: Undecided => Medium
** Changed in: linux (Ubuntu Bionic)
Status: New => Triaged
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https://bugs.launchpad.net/bugs/1771620
Title:
Hang on network interface removal in Xen virtual machine
Status in linux package in Ubuntu:
Triaged
Status in linux source package in Bionic:
Triaged
Bug description:
On a hosting platform running Xen hypervisor, in a virtual machine
with Ubuntu 18.04 system and the default kernel from Ubuntu, I try to
detach a virtual network interface. On the Xen side, the virtual
interface is removed from the VM but the kernel still has the
interface. Then a couple of minutes afterwards, the kernel log show
this kernel trace:
INFO: task xenwatch:108 blocked for more than 120 seconds.
Tainted: G W 4.15.0-20-generic #21-Ubuntu
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
xenwatch D 0 108 2 0x80000000
Call Trace:
__schedule+0x297/0x8b0
schedule+0x2c/0x80
xennet_remove+0xda/0x1c0
? wait_woken+0x80/0x80
xenbus_dev_remove+0x54/0xa0
device_release_driver_internal+0x15b/0x220
device_release_driver+0x12/0x20
bus_remove_device+0xec/0x160
? xenbus_otherend_changed+0x110/0x110
device_del+0x13d/0x360
? xenbus_otherend_changed+0x110/0x110
? xenbus_otherend_changed+0x110/0x110
device_unregister+0x1a/0x60
xenbus_dev_changed+0xa3/0x1e0
? xenwatch_thread+0xcc/0x160
frontend_changed+0x21/0x50
xenwatch_thread+0xc4/0x160
? wait_woken+0x80/0x80
kthread+0x121/0x140
? find_watch+0x40/0x40
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x35/0x40
In the git repository of Linux, the commit
c2d2e6738a209f0f9dffa2dc8e7292fc45360d61 (xen-netfront: Fix hang on
device removal)
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c2d2e6738a209f0f9dffa2dc8e7292fc45360d61
seems to be related to this situation.
I rebuilded the Ubuntu kernel from the package source and applied this
patch. Once the VM has booted with the new kernel, I was able to
remove network interface without hangs from the kernel.
I also booted the VM with the Ubuntu kernel 4.13.0-42-generic and was
able to remove the network interface with success.
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.15.0-20-generic 4.15.0-20.21
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
Date: Wed May 16 16:36:06 2018
ProcEnviron:
TERM=rxvt-unicode
PATH=(custom, no user)
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: linux-signed
UpgradeStatus: No upgrade log present (probably fresh install)
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