[Bug 1435080] [NEW] mysql-server upgrade hangs dpkg --reconfigure (if root password is set?)

[Shevek]

Public bug reported:

1) apt-get dist-upgrade
2) Give mysql password to dpkg as requested in curses dialog
3) process hangs/crashes/something

Now, apt-get says it wants me to run this, but:
shevek at raven:~$ sudo dpkg --configure -a
Setting up mysql-server-5.6 (5.6.23-1~exp1~ubuntu3) ...
<hangs>

Here is the dpkg pstree:
4     0 11389  4416  20   0  56668  3748 poll_s S+   pts/9      0:00  \_ sudo dpkg --configure -a
4     0 11390 11389  20   0  24680  9192 wait   S+   pts/9      0:00      \_ dpkg --configure -a
0     0 11391 11390  20   0  64536 17248 wait   S+   pts/9      0:00          \_ /usr/bin/perl -w /usr/share/debconf/frontend /var/lib/dpkg/info/mysql-server-5.6.postinst configure 
4     0 11401 11391  20   0  12596  3280 wait   S+   pts/9      0:00              \_ /bin/bash /var/lib/dpkg/info/mysql-server-5.6.postinst configure 
0     0 11492 11401  20   0   4472  1620 wait   S+   pts/9      0:00                  \_ /bin/sh /usr/sbin/invoke-rc.d mysql start
4     0 11534 11492  20   0  23960  2712 poll_s S+   pts/9      0:00                      \_ systemctl start mysql.service

And here is something else which may be related:
4     0 11539     1  20   0  12480  2984 wait   Ss   ?          0:00 /bin/bash /usr/share/mysql/mysql-systemd-start post
0     0 12882 11539  20   0   7228   728 ?      S    ?          0:00  \_ sleep 1

System does not respond well to this process being killed.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: mysql-server-5.6 5.6.23-1~exp1~ubuntu3
ProcVersionSignature: Ubuntu 3.19.0-9.9-generic 3.19.1
Uname: Linux 3.19.0-9-generic x86_64
ApportVersion: 2.16.2-0ubuntu4
Architecture: amd64
CurrentDesktop: XFCE
Date: Sun Mar 22 14:15:34 2015
InstallationDate: Installed on 2015-03-05 (17 days ago)
InstallationMedia: Xubuntu 14.04.2 LTS "Trusty Tahr" - Release amd64 (20150218.1)
SourcePackage: mysql-5.6
UpgradeStatus: Upgraded to vivid on 2015-03-19 (3 days ago)

** Affects: mysql-5.6 (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug vivid

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Title:
  mysql-server upgrade hangs dpkg --reconfigure (if root password is
  set?)

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