Comment 16 for bug 1551811

I (with tvoss' help) created some tools to recreate the scenario in a more controlled setup (e.g. no Qt). I have tested the trusted prompt feature at the mir level, as well as the unity8 level, with Camera app and with other apps. I haven't been able to repro the issue after thousands of iterations.

It involves running the camera unconfined like so :
phablet@ubuntu-phablet:/usr/share/click/preinstalled/com.ubuntu.camera/current$ ./camera-app --desktop_file_hint=dialer-app

and then running the following in a script doing thousands of iterations :
mir_demo_client_prompt_helper_provider.bin -p <camera-pid> -m /run/user/32011/mir_socket_trusted -- --desktop_file_hint=dialer-app

mir_demo_client_prompt_helper_provider.bin sets up a trust session and forks a gl app (simulating the dialog box) that renders 20 frames and exits (so it could be run automatically.

This setup didn't yield any panic or crash.

One thing I haven't tried is using trivial code (no Qt) as the actual TPP - this way the timing that TPP cutting in right before Camera starts to render can be recreated. Whereas the above case requires the Camera app to have been launched and rendering already. This involves modifying the lp:trust-store code that I'm not familiar with, but with some help, am willing to give it a try.