Unity 8 crash when exiting an X app

[Christopher Townsend]

seeing this with just packages in the archive, no extra ppas

With the latest qtmir (0.4.6+16.04.20151125-0ubuntu1) and unity 8 (8.11+16.04.20151126-0ubuntu1) packages on Xenial, when exiting an X app, the Unity 8 session "stops". I have seen it either go to the blank u-s-c screen or back to the Unity 8 greeter.

I don't have a crash file nor have I seen any interesting info in the unity8.log. If downgrade qtmir to 0.4.6+16.04.20151119-0ubuntu1 and unity 8 to 8.11+16.04.20151112.1, the issue no longer occurs.

When I get the blank u-s-c screen, I do see this in the application log:

[1449081140.172725] <ERROR> MirSurfaceAPI: Caught exception at client library boundary (in mir_surface_release): /build/mir-sTjxjQ/mir-0.17.1+16.04.20151105.1/src/client/rpc/stream_socket_transport.cpp(168): Throw in function virtual void mir::client::rpc::StreamSocketTransport::send_message(const std::vector<unsigned char>&, const std::vector<mir::Fd>&)
Dynamic exception type: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<mir::socket_disconnected_error> >
std::exception::what: Failed to send message to server: Broken pipe
32, "Broken pipe"
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<mir::socket_disconnected_error> >'
  what(): Failed to send message to server: Broken pipe

[kevin gunn (kgunn72)]

Strangely, if Xapps are "quit" in non-windowed mode, as in "swiped" away in spread - there is no freeze. all is ok.

[Christopher Townsend (townsend)]

Here's the output when running 'sudo gdb program `pidof unity8`:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7f58091bf700 (LWP 10614)]
0x00007f581e754e8e in SurfaceObserver::createQCursorFromMirCursorImage(mir::graphics::CursorImage const&) () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqpa-mirserver.so

[Michał Sawicz (saviq)]

Narrowed down to:

QCursor SurfaceObserver::createQCursorFromMirCursorImage(const mir::graphics::CursorImage &cursorImage) {
    if (cursorImage.as_argb_8888() == nullptr) {

cursorImage is 0x0, trying to find out if that's expected.

[Michał Sawicz (saviq)]

<anpok> Saviq: not expected..

[Michał Sawicz (saviq)]

Looks like this could be dupe of bug #1521795, there's an approved branch already, will require an update to qtmir's SurfaceObserver.