unity8 hang w/ CPU pegged

[Selene ToyKeeper]

To trigger:
1. Wipe (or freshly flash) rc-proposed on a krillin or mako
2. Log in, configure time zone
3. Tilt the phone to make the screen rotate

At this point, the UI stopped responding and 'top' showed 100% CPU being used by unity8.

I tried to get data from gdb, but it wasn't very helpful:
(gdb) bt
#0 0xa803cce2 in ?? ()
#1 0xa803cb98 in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

More details are needed.

[Jean-Baptiste Lallement (jibel)]

I experienced a similar issue very frequently with silo 13 (unity8, new OOBE) but never without. So maybe the issue already exists in the image but silo 13 makes it worse.

[Lukáš Tinkl (lukas-kde)]

I just got the hang by simply configuring the timezone in System Settings. SIlo 13 might be making it worse in that in configures the TZ as well.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Lukáš Tinkl (lukas-kde)]

Just reproduced on mako with plain rc-proposed: http://paste.ubuntu.com/15470993/

[Michał Sawicz (saviq)]

I've tracked it down to this indicator-datetime landing:

https://requests.ci-train.ubuntu.com/#/ticket/893

Downgrading indicator-datetime to the version below (or simply stopping it before following the repro steps above) prevents the freeze.

https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/stable-phone-overlay/+sourcepub/5495431/+listing-archive-extra

[Michał Sawicz (saviq)]

It's most probably the addition of calendar to the indicator that caused this, so we might revert that for the time being, until we understand what the issue is.

[Michał Sawicz (saviq)]

Note the landing above is not just the MPs it lists, since the two previous releases of indicator-datetime were xenial-only - the full diff between the two vivid overlay versions is, I believe, here:

https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/stable-phone-overlay/+sourcepub/6208703/+listing-archive-extra

[Charles Kerr (charlesk)]

Looks like this is being caused by the QML calendar widget: I can consistently reproduce the freeze using ToyKeeper's recipe of wipe+timezone+rotate on a freshly-flashed krillin running rc-proposed. The freeze goes away for me after installing the linked branch from silo 70, which removes the calendar.

This is a u8 bug rather than an indicator-datetime one, but this is the easiest place to back out the calendar for OTA10.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Launchpad Janitor (janitor)]

This bug was fixed in the package indicator-datetime - 15.10+16.04.20160323-0ubuntu1

---------------
indicator-datetime (15.10+16.04.20160323-0ubuntu1) xenial; urgency=medium

  [ Charles Kerr ]
  * Remove the calendar from the phone profile. (LP: #1560188)

 -- Michael Zanetti <email address hidden> Wed, 23 Mar 2016 09:45:27 +0000

[Launchpad Janitor (janitor)]

This bug was fixed in the package ubuntu-settings-components - 0.7+16.10.20160617-0ubuntu1

---------------
ubuntu-settings-components (0.7+16.10.20160617-0ubuntu1) yakkety; urgency=medium

  [ Lukáš Tinkl ]
  * Fix huge icons in network indicator caused by a binding loop (LP:
    #1585645, #1586667)

  [ Nick Dedekind ]
  * Removed some of the timezone sensitive date code from calendar (LP:
    #1450036, #1560188)

 -- Michał Sawicz <email address hidden> Fri, 17 Jun 2016 13:02:37 +0000