Qemu 1:6.2+dfsg-2ubuntu6 deadlock bug

There is a known bug that will cause VM deadlock, the patch should be merged and released:

https://gitlab.com/qemu-project/qemu/-/commit/1dbbe6f172810026c51dc84ed927a3cc23017949#841723aa93098d8ab3b5068795e10ae7cf2a3179

That's clearly a fix for a bug, but I couldn't identify an upstream issue which describes the problem. The commit message has:

  Fixes: 0bf41cab

but that's a reference to another commit, not to an issue. Finding original description of the bug would help identifying a test case for the SRU.

@xp are you able to point us to the upstream bug report, or to provide steps to reproduce the issue which we can use to verify the fix?

I'm marking this as Incomplete for now because the description of the problem is too vague, but I think this will become a valid SRU case.

This should be the upstream bug report:
https://gitlab.com/qemu-project/qemu/-/issues/807


Thanks, that report also has nice steps to reproduce. I updated the bug tags/status accordingly.

Thanks

From the description this bug affects Jammy and Kinetic, so I added explicit tasks for each series.

Thanks this is great pre-work and a patch on a plate.
I was pondering if I should wait until we merge qemu 7.0 for kintic, but that would delay this too much.

I still need to find some time, but I'll prepare and upload the fix without waiting for 7.0.

FYI - I have prepared a PPA and merge proposals for the related Ubuntu package changes:

PPA: https://launchpad.net/~paelzer/+archive/ubuntu/lp-1970563-vnc-deadlock
Jammy: https://code.launchpad.net/~paelzer/ubuntu/+source/qemu/+git/qemu/+merge/422947
Kinetic: https://code.launchpad.net/~paelzer/ubuntu/+source/qemu/+git/qemu/+merge/422946

Thanks for the Review Sergio.

Uploaded the fix for Kinetic.
We can start the SRU to jammy once it is complete there.

This bug was fixed in the package qemu - 1:6.2+dfsg-2ubuntu7

---------------
qemu (1:6.2+dfsg-2ubuntu7) kinetic; urgency=medium

  * d/p/u/lp-1970563-ui-vnc.c-Fixed-a-deadlock-bug.patch: avoid deadlock
    in vnc connections (LP: #1970563)

 -- Christian Ehrhardt <email address hidden>  Thu, 19 May 2022 08:25:20 +0200

Completed in Kinetic, uploaded to Jammy now - waiting for the SRU team to have a look

Hello xp, or anyone else affected,

Accepted qemu into jammy-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/qemu/1:6.2+dfsg-2ubuntu6.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.  Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-jammy to verification-done-jammy. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-jammy. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

All autopkgtests for the newly accepted qemu (1:6.2+dfsg-2ubuntu6.1) for jammy have finished running.
The following regressions have been reported in tests triggered by the package:

vagrant-mutate/1.2.0-4.1 (s390x, ppc64el)
livecd-rootfs/2.764 (arm64, ppc64el)
ubuntu-image/2.2+22.04ubuntu3 (arm64, s390x)
sbuild/0.81.2ubuntu6 (s390x, ppc64el)
edk2/2022.02-3 (armhf)
initramfs-tools/0.140ubuntu13 (amd64)
systemd/249.11-0ubuntu3.1 (ppc64el)


Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/jammy/update_excuses.html#qemu

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!


FYI: Autopkgtest issues resolved, but verification of the upload for the presented problem is needed.

@XP - it is always best to do this in the original reported environment - do you think you could do that verification?

Sure, This my test steps:
* start a qemu wit qemu vnc
   qemu-system-x86_64 -vnc 127.0.0.1:0 ...

* Connect and disconnect and connect with VNC against it (We use novnc).

* when qemu-system-x86 1:6.2+dfsg-2ubuntu6
	occur which deadlocks qemu - no interaction is possible anymore

* upgrade to qemu-system-x86/jammy-proposed 1:6.2+dfsg-2ubuntu6.1
    Connect and disconnect and connect, everything is ok， no more deadlock

The bug has been fixed, thank you.

Perfect, thank you Xiongpeng!

The verification of the Stable Release Update for qemu has completed successfully and the package is now being released to -updates.  Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report.  In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

This bug was fixed in the package qemu - 1:6.2+dfsg-2ubuntu6.1

---------------
qemu (1:6.2+dfsg-2ubuntu6.1) jammy; urgency=medium

  * d/p/u/lp-1970563-ui-vnc.c-Fixed-a-deadlock-bug.patch: avoid deadlock
    in vnc connections (LP: #1970563)

 -- Christian Ehrhardt <email address hidden>  Thu, 19 May 2022 08:25:20 +0200