Comment 4 for bug 1515712

Any Qt code that uses QNetworkAccessManager, QNetworkSession, or related classes can cause the QNetwork Bearer Management to get instantiated, which in turn loads a network-manager specific plugin. Please see bug #1480877 for details. As it's really long, you might want to check out just the following comments:

https://bugs.launchpad.net/ubuntu-rtm/+source/location-service/+bug/1480877/comments/65
https://bugs.launchpad.net/ubuntu-rtm/+source/location-service/+bug/1480877/comments/68

Besides the problems with match rules that are described in the bug, we also discovered that there's quite a bit of blocking DBus logic in this bearer mgmt plugin.

We have an updated version of this plugin available for testing in silo-026, which also contains some location-services DBus fixes as well. If you want, you can just install the qtbase network package:

https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/landing-026/+files/libqt5network5_5.4.1%2Bdfsg-2ubuntu11%7Evivid1%7Etest1_armhf.deb

We basically removed much of the code that pays attention to NM access points and devices, which included a good portion of the blocking DBus calls that were being made. That said, not all were removed, so there still might be the potential for lockup...