Difficult to say without a stack trace, but I expect this to be bug #1401488, one thing to notice is whether you get a .crash file for unity-system-compositor in /var/crash.
** Changed in: unity8 (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to unity8 in Ubuntu. https://bugs.launchpad.net/bugs/1405687 Title: unity8 crashes while using webbrowser-app Status in unity8 package in Ubuntu: Incomplete Bug description: This happens often, maybe one every ten minutes while browsing (m.reddit.com, en.wikipedia.org, bt.no, stackexchange.com, etc). 1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu Distributor ID: Ubuntu Description: Ubuntu Vivid Vervet (development branch) Release: 15.04 (r58) Codename: vivid 2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center unity8: Installed: 8.02+15.04.20141216.1-0ubuntu1 Candidate: 8.02+15.04.20141216.1-0ubuntu1 Version table: *** 8.02+15.04.20141216.1-0ubuntu1 0 500 http://ports.ubuntu.com/ubuntu-ports/ vivid/universe armhf Packages 100 /var/lib/dpkg/status 3) What you expected to happen Unity8/mir should not crash 4) What happened instead Something crashed, got spinning Ubuntu logo Excerpt from unity8 log from before, during and after the crash, while browsing the web normally (one tab, wikipedia): qtmir.applications: Application::setSession - appId= "webbrowser-app" session= QObject(0x0) qtmir.sessions: Session::setSurface - session= "QtUbuntu" surface= QQuickItem(0) qtmir.surfaces: MirSurfaceItem::~MirSurfaceItem - this= qtmir::MirSurfaceItem (this = 0x18f1240 , name= "" , parent = 0x1804438 , geometry = QRectF(0,0 768x1222) , z = 1 ) qtmir.sessions: SessionManager::onSessionStopping - sessionName= QtUbuntu qtmir.mir: SessionListener::destroying_surface - this= SessionListener(0xb04667d4) session= 0xad5068dc surface= 0xad507568 qtmir.surfaces: MirSurfaceManager::onSessionDestroyingSurface - session= 0xad5068dc surface= 0xad507568 surface.name= Ubuntu Web Browser MirSurfaceManager::onSessionDestroyingSurface: unable to find MirSurfaceItem corresponding to surface= 0xad507568 surface.name= Ubuntu Web Browser Signal caught by Mir, stopping Mir server.. qtmir.applications: ApplicationManager::onSessionStopping - sessionName= pay-service qtmir.sessions: SessionManager::onSessionStopping - sessionName= pay-service qtmir.applications: ApplicationManager::onSessionStopping - sessionName= UbuntuLocationService qtmir.sessions: SessionManager::onSessionStopping - sessionName= UbuntuLocationService Caught exception at Mir/EGL driver boundary: /build/buildd/mir-0.9.0+15.04.20141125/src/client/rpc/stream_socket_transport.cpp(166): Throw in function virtual void mir::client::rpc::StreamSocketTransport::send_message(const std::vector<unsigned char>&, const std::vector<mir::Fd>&) Dynamic exception type: N5boost16exception_detail10clone_implINS0_19error_info_injectorIN3mir25socket_disconnected_errorEEEEE std::exception::what: Failed to send message to server: Broken pipe 32, "Broken pipe" qtmir.mir: SessionListener::stopping - this= SessionListener(0xb04667d4) session= 0xad5035fc qtmir.mir: SessionListener::unfocused - this= SessionListener(0xb04667d4) g_dbus_connection_real_closed: Remote peer vanished with error: Underlying GIOStream returned 0 bytes on an async read (g-io-error-quark, 0). Exiting. [1419545181.094743] (II) UnknownComponent: Stopping Mir Server Signal caught by Mir, stopping Mir server.. QtCompositor::setAllWindowsExposed false qtmir.surfaces: MirSurfaceItem::release - this= qtmir::MirSurfaceItem (this = 0x16c6c50 , name= "" , parent = 0x0 , geometry = QRectF(0,0 768x1222) , z = 0 ) qtmir.sessions: Session::setSurface - session= "QtUbuntu" surface= QQuickItem(0) QThread: Destroyed while thread is still running (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed (process:31750): GLib-CRITICAL **: g_variant_unref: assertion 'value->ref_count > 0' failed qtmir.surfaces: MirSurfaceItem::~MirSurfaceItem - this= qtmir::MirSurfaceItem (this = 0x16c6c50 , name= "" , parent = 0x0 , geometry = QRectF(0,0 768x1222) , z = 0 ) qtmir.applications: ApplicationManager::~ApplicationManager qtmir.sessions: SessionManager::~SessionManager - this= qtmir::SessionManager(0x12ec678, name = "qtmir::SessionManager") qtmir.surfaces: MirSurfaceManager::~MirSurfaceManager - this= qtmir::MirSurfaceManager(0x12ecf30, name = "qtmir::SurfaceManager") Attempted to unregister path (path[0] = core path[1] = ubuntu) which isn't registered process 31750: arguments to dbus_connection_close() were incorrect, assertion "connection->generation == _dbus_current_generation" failed in file ../../dbus/dbus-connection.c line 2935. This is normally a bug in some application using the D-Bus library. process 31750: arguments to dbus_connection_unref() were incorrect, assertion "connection->generation == _dbus_current_generation" failed in file ../../dbus/dbus-connection.c line 2822. This is normally a bug in some application using the D-Bus library. process 31750: arguments to dbus_message_unref() were incorrect, assertion "message->generation == _dbus_current_generation" failed in file ../../dbus/dbus-message.c line 1695. This is normally a bug in some application using the D-Bus library. process 31750: arguments to dbus_connection_unref() were incorrect, assertion "connection->generation == _dbus_current_generation" failed in file ../../dbus/dbus-connection.c line 2822. This is normally a bug in some application using the D-Bus library. process 31750: arguments to dbus_message_unref() were incorrect, assertion "message->generation == _dbus_current_generation" failed in file ../../dbus/dbus-message.c line 1695. This is normally a bug in some application using the D-Bus library. process 31750: arguments to dbus_connection_unref() were incorrect, assertion "connection->generation == _dbus_current_generation" failed in file ../../dbus/dbus-connection.c line 2822. This is normally a bug in some application using the D-Bus library. () [1419545193.991218] (II) UnknownComponent: Loading library : libmirplatform4driver.so qtmir.mir: MirServer created [1419545194.035076] (II) UnknownComponent: Starting Mir server ProblemType: Bug DistroRelease: Ubuntu 15.04 Package: unity8 8.02+15.04.20141216.1-0ubuntu1 Uname: Linux 3.4.0-5-mako armv7l ApportVersion: 2.15-0ubuntu3 Architecture: armhf Date: Thu Dec 25 23:10:07 2014 InstallationDate: Installed on 2014-12-18 (7 days ago) InstallationMedia: Ubuntu Vivid Vervet (development branch) - armhf (20141218-020204) SourcePackage: unity8 UpgradeStatus: No upgrade log present (probably fresh install) upstart.unity8.log: qtmir.sensor: Screen::toggleSensors - enable= false To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity8/+bug/1405687/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp