pulseaudio crashed with SIGABRT in pa_alsa_path_set_volume() from source_write_volume_cb() from source_set_port_cb() from pa_source_process_msg() from source_process_msg()

https://errors.ubuntu.com/problem/3bb5044276ea358334e8e662559a1cbd45240cd9

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[Impact]
pulseaudio daemon crashes, interrupting sound output/input.

[Test Case]
Theoretical test case (crash does not happen for all users):
1. Find some headphones and/or microphone. Ensure you do not wear the
   headphones during the test as it may be loud.
2. Set audio output/input volumes to maximum.
3. Unplug and replug the headphones/microphone.
4. Check that that pulseaudio process is still running, with a start time
   older than when you began this test case.

[Regression Potential]
Low. This SRU affects the pulseaudio daemon only so the worst case would be loss of sound output/input. The same patches have been released to
17.10 for a month already and zero regressions of the crashes have
occurred worldwide since then.

[Other Info]
Debdiff patch is attached to the most prolific bug 1539209.

[Original Description]

This error is there when i get back to the computer after a while of no use, and at login after restart. haven't seen this error while the system is "active"/in use.

I have been unable to provoke the error to come.

I'm not sure it is related, but when i plug in a headset, the audio volume goes through the roof, and a loud (painfully so) scratching sound is coming from the headset until i press Vol+. Vol- does nothing till i have pressed up at least once.
But the bug report thing does not pop up when the sound issue is there.

Description: Ubuntu Xenial Xerus (development branch)
Release: 16.04

pulseaudio:
  Installed: 1:8.0-0ubuntu2
  Candidate: 1:8.0-0ubuntu2
  Version table:
 *** 1:8.0-0ubuntu2 500
        500 http://dk.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Crash
DistroRelease: Ubuntu 16.04
Package: pulseaudio 1:8.0-0ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-15.31-generic 4.4.6
Uname: Linux 4.4.0-15-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_modeset nvidia
ApportVersion: 2.20-0ubuntu3
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: tbs 22776 F.... pulseaudio
CrashCounter: 1
CurrentDesktop: Unity
Date: Mon Mar 28 12:39:45 2016
ExecutablePath: /usr/bin/pulseaudio
InstallationDate: Installed on 2016-01-14 (73 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
ProcCmdline: /usr/bin/pulseaudio --start --log-target=syslog
Signal: 6
SourcePackage: pulseaudio
StacktraceTop:
 pa_alsa_path_set_volume () from /usr/lib/pulse-8.0/modules/libalsa-util.so
 ?? () from /usr/lib/pulse-8.0/modules/libalsa-util.so
 ?? () from /usr/lib/pulse-8.0/modules/libalsa-util.so
 pa_source_process_msg () from /usr/lib/x86_64-linux-gnu/pulseaudio/libpulsecore-8.0.so
 ?? () from /usr/lib/pulse-8.0/modules/libalsa-util.so
Title: pulseaudio crashed with SIGABRT in pa_alsa_path_set_volume()
UpgradeStatus: Upgraded to xenial on 2016-03-19 (8 days ago)
UserGroups: adm cdrom dialout dip lp lpadmin plugdev root sambashare sudo vboxusers
dmi.bios.date: 09/18/2015
dmi.bios.vendor: LENOVO
dmi.bios.version: G5ETA3WW (2.63 )
dmi.board.asset.tag: Not Available
dmi.board.name: 244743G
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG5ETA3WW(2.63):bd09/18/2015:svnLENOVO:pn244743G:pvrThinkPadW530:rvnLENOVO:rn244743G:rvrNotDefined:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 244743G
dmi.product.version: ThinkPad W530
dmi.sys.vendor: LENOVO