[SRU] Loss of USB device causes zita-ajbridge to run cpu at 100% and hang

[Len Ovens]

[Impact]

 * zita-ajbridge allows bridging extra alsa devices to jackd as a client.
   If that extra device is a USB device and is unplugged, the bridge uses
   100% cpu and slows the rest of the system to a crawl. The only way to
   stop this process is with a kill -9.

[Test Case]

 * Using (Ubuntu) Studio Controls, start Jack with built-in sound card and
   a USB device.

 * Unplug USB device. Bridge will now use 100% CPU process and stall the
   system.

[Regression Potential]

 * The upstream version has one single change consisting of the bugfix to
   prevent the 100% CPU usage on disconnect. While it is possible that
   this fix doesn't do what it advertises, the regression potential here
   is slim to none.

[Additional Info]

 * As already noted, this fix is already in Groovy.

Original bug report follows:

zita-ajbridge allows bridging extra alsa devices to jackd as a client. If that extra device is a USB device and is unplugged, the bridge uses 100% cpu and slows the rest of the system to a crawl. The only way to stop this process is with a kill -9.

However, there is already a bugfix release upstream. The release notes for version 0.8.4 (which is already in Groovy) are only one line:
"zita-ajbridge 0.8.4     (05/04/2020)

* Fixed 100% CPU on sound card disconnect.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: zita-ajbridge 0.8.2-1
ProcVersionSignature: Ubuntu 5.4.0-42.46-lowlatency 5.4.44
Uname: Linux 5.4.0-42-lowlatency x86_64
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Mon Jul 27 20:28:00 2020
InstallationDate: Installed on 2020-04-23 (96 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200422)
SourcePackage: zita-ajbridge
UpgradeStatus: No upgrade log present (probably fresh install)

[Brian Murray (brian-murray)]

Hello Len, or anyone else affected,

Accepted zita-ajbridge into focal-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/zita-ajbridge/0.8.4-1ubuntu0.20.04.1 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-focal to verification-done-focal. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-focal. 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.

[Len Ovens (len-ovenwerks)]

Tested new package from proposed. Run Jackdbus, Run zita-j2a with USB device plugged in. That device shows up on the jack graph and will take connections. Start htop and show zita processes. Remove USB device while watching htop. Cpu use remains stable at .5 to 2% (same as running normally). Device remains on the graph (normal) which allows studio-controls time to switch connections to another device before kill SIGINT zita process.

So the bug fix does correct the problem of high cpu
The bug fix does not cause any other regressions in the software that relies on zita-ajbridge

[Łukasz Zemczak (sil2100)]

Note for the future: please provide the exact package version number used for verification.

[Launchpad Janitor (janitor)]

This bug was fixed in the package zita-ajbridge - 0.8.4-1ubuntu0.20.04.1

---------------
zita-ajbridge (0.8.4-1ubuntu0.20.04.1) focal; urgency=medium

  * SRU for Focal, fixes 100% CPU usage bug (LP: #1889146)

 -- Erich Eickmeyer <email address hidden> Tue, 28 Jul 2020 09:12:18 -0700

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for zita-ajbridge 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.