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[Tony Espy <1480877@xxxxxxxxxxxxxxxxxx>]

A bit more info...

After a deeper look at some DBus traces on a vanilla krillin OTA6 image,
I noticed a few more things.

After a ScanDone signal gets sent by NM, you typically see 3-5
PropertiesChanged signals for new APs that include all of the
properties.  Then, you see a PropertiesChanged from Device.Wireless
which includes an array of the current APs.  Then you usually see a
PropertiesChanged signal for every AP except current ( AP=0 ), with the
property 'LastSeen'.  These signals  all typically have the same value
for last-seen, although if the list is long, there might be variation of
maybe +1-2 across all the signals.

What's unusual, is I'm then seeing what looks like a second set of
PropertiesChanged signals for all of the current APs.

Digging deeper in the trace, it turns out wpa_supplicant actually
generates two PropertiesChanged signals every time an object changes.
It first uses the new ( more correct ) 'org.freedesktop.DBus.Properties'
interface, then sends the signal *again* using the deprecated
'fi.w1.wpa_supplicant1.Interface'!  I think this is what in turn
triggers the second signal for each AP from NM.  I haven't proven this
100% yet, but it certainly explains the behavior of NM.

I'll continue to test.

I also had a discussion with one of our location service engineers, and
we think that it might be possible to get rid of the 'LastSeen'
PropertiesChanged signals altogether and just use the Device.Wireless
'AccessPoints' property, which gets updated after every scan completes.

-- 
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https://bugs.launchpad.net/bugs/1480877

Title:
  Access points' "PropertiesChanged" dbus signals freeze UI on mobile
  devices

Status in Canonical System Image:
  Confirmed
Status in indicator-network package in Ubuntu:
  Incomplete
Status in network-manager package in Ubuntu:
  Incomplete

Bug description:
  Krillin, rc-proposed, r83

  
  DESCRIPTION:
  I've been trying to track down the cause of the occasional UI freezes on my Krillin device, and I noticed that whenever the UI freezes for 2-4 seconds, I get a burst of "PropertiesChanged" signals in dbus-monitor

  Here's a log of what's shown in dbus-monitor:
  http://pastebin.ubuntu.com/11992322/

  I'd guess the problem is in the code that actually catches the signals
  and acts accordingly.

  HOW TO REPRODUCE: 
  1) Move to a place where many wifi hotspots are available
  2) Connect the device via USB and run "phablet-shell" and then "dbus-monitor"
  3) Use the device while keeping an eye on dbus-monitor output

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