xenbus: Avoid deadlock during suspend due to open transactions

[Doug Goldstein]

[Impact]
Xen guests may hang during resume after a migration or suspend.

[Test Case]
Create a Xen guest and run this script and then suspending the VM:

    import pyxs, time
    c = pyxs.client.Client(xen_bus_path="/dev/xen/xenbus")
    c.connect()
    c.transaction()
    time.sleep(3600)

[Fix]
The following upstream commit fixes the issue:

"xenbus: Avoid deadlock during suspend due to open transactions"
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d10e0cc113c9e1b64b5c6e3db37b5c839794f3df

[Doug Goldstein (cardoe)]

This is fixed in bionic with Ubuntu-4.15.0-59.66. Looking to get this ported into xenial.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1845033

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Bob Ball (bob-ball)]

This is equivalent to 1844421

[Po-Hsu Lin (cypressyew)]

Thanks for the bug report, this has been applied to the master-next branch of:
  * Disco - https://kernel.ubuntu.com/git/ubuntu/ubuntu-disco.git/commit/?h=master-next&id=e156b3ed11e418de90b15389a6af7187ace0184b

It's scheduled to be released on the next SRU cycle,

And the master branch of:
  * Bionic - https://kernel.ubuntu.com/git/ubuntu/ubuntu-bionic.git/commit/?h=master-next&id=683f56d305988dda311e928fba080edb758c8d13
  * Eoan - https://kernel.ubuntu.com/git/ubuntu/ubuntu-eoan.git/commit/?h=master-next&id=d10e0cc113c9e1b64b5c6e3db37b5c839794f3df

Therefor I will mark this as a duplicate of bug 1840076 to keep track of the release status.

[Po-Hsu Lin (cypressyew)]

Link correction for master branch:
  * Bionic - https://kernel.ubuntu.com/git/ubuntu/ubuntu-bionic.git/commit/?h=master&id=683f56d305988dda311e928fba080edb758c8d13
  * Eoan - https://kernel.ubuntu.com/git/ubuntu/ubuntu-eoan.git/commit/?h=master&id=d10e0cc113c9e1b64b5c6e3db37b5c839794f3df

[Vincent Fortier (th0ma7)]

Bug entry #1845033 also affects Xenial (16.04) and Trusty (14.04 HWE) v4.4 kernels.
Is it possible to backport the fix to 4.4 kernels as well?
Actually I believe this should have been material for 4.4/4.9 mainline stable trees in the first place.

Relates to following fix:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.2.21&id=d10e0cc113c9e1b64b5c6e3db37b5c839794f3df

[Kamal Mostafa (kamalmostafa)]

I have set this bug as "not a duplicate", in order to track the request to have the fix backported to the 4.4 kernels (Xenial and Trusty-hwe ).