Unable to enter password in the lock screen after using Qtcreator to run apps on the device

[Nekhelesh Ramananthan]

I have noticed consistently that after upgrading the phone to vivid, while developing apps and running them on the device via Qtcreator, after a few runs, when the device locks (due to timeout, or manual locking) it is no longer possible to unlock the device by typing in the password in the lock screen since when I type the password, the passphrase characters are not typed into the textfield. It is sort of like the lock screen does not take any input. The only way to fix the solution is to reboot the phone since I cannot adb into the device without unlocking it first to do any unity8 reboots.

I noticed that I get the following output line on Qtc, Connection to 127.0.0.1 closed by remote host. I tried using 2 other cables and have noticed the connection closed by remote host. But despite the remote host closing the connection, QtC still displays the device status in green indicating it is detected and available. However on trying to run the app again, I get the error "Could not conenct to host: Connection refused. Is the device still connected and set up network access?"

This connection is terminated by remote host after few seconds even if I let the app be idle during that time.

Steps to reproduce the issue:
1. Connect the phone to the laptop.
2. Open any app in Qtcreator and set it to run the app on the device.
3. Run the app on the device.
4. Close the app on the phone and lock the device.
5. Try unlocking the device.

What happens:
Device is locked and the lock screen textfield does not accept any input. Pressing on the keypad buttons doesnt do anything

Note: The lockscreen issue happens only on vivid. But the connection being terminated by the remote host happens both on vivid and rtm.

System Information:
Laptop: Ubuntu 14.04.2 LTS
Nexus 4(Mako) running vivid img 125
qtcreator-plugin-ubuntu: 3.1.1+15.04.20150224-0ubuntu1~0trusty1

[Nekhelesh Ramananthan (nik90)]

I noticed that I get the following output line on Qtc, Connection to 127.0.0.1 closed by remote host. I tried using 2 other cables and have noticed the connection closed by remote host. But despite the remote host closing the connection, QtC still displays the device status in green indicating it is detected and available. However on trying to run the app again, I get the error "Could not conenct to host: Connection refused. Is the device still connected and set up network access?"

[Benjamin Zeller (zeller-benjamin)]

I'm not sure the lockup of the screen is actually a qtcreator-plugin-ubuntu bug, since its not
present on krillin as you said.

If a SSH connection to the device is active or not does not change the device connection
state, because USB is used to detect if a device is attached or not. However the new policies
for ADB when the device is locked might make connections to the device fail. In that case
ADB will just refuse connections, thats also the reason why the device will not be detected
when its locked and attached for the first time.

[Benjamin Zeller (zeller-benjamin)]

A workaround is to log into the phone with SSH/adb and restart lightdm.

[Nekhelesh Ramananthan (nik90)]

Well I don't know if this bug is not present on krillin or not since I dont have that device. I will try out workaround to see if that works.

[Launchpad Janitor (janitor)]

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