DisplayWindow::makeCurrent crash with xmir apps

[Christopher Townsend]

This crash occurs when opening an Xmir window and leaving it idle for ~5-10 minutes.

If you need steps to reproduce, please ping me.

ProblemType: Crash
DistroRelease: Ubuntu 15.04
Package: unity8 8.02+15.04.20150109.2-0ubuntu1
ProcVersionSignature: Ubuntu 3.18.0-8.9-generic 3.18.1
Uname: Linux 3.18.0-8-generic x86_64
ApportVersion: 2.15.1-0ubuntu2
Architecture: amd64
CrashCounter: 1
Date: Tue Jan 13 11:57:45 2015
ExecutablePath: /usr/bin/unity8
ExecutableTimestamp: 1420800924
InstallationDate: Installed on 2013-03-18 (666 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
ProcCmdline: unity8
ProcCwd: /home/townsend
ProcEnviron:
 LANGUAGE=en_US
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SegvAnalysis:
 Segfault happened at: 0x7fb06a6fc357 <_ZN13DisplayWindow11makeCurrentEv+27>: mov (%rax),%rax
 PC (0x7fb06a6fc357) ok
 source "(%rax)" (0x00000030) not located in a known VMA region (needed readable region)!
 destination "%rax" ok
 Stack memory exhausted (SP below stack segment)
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: unity8
StacktraceTop:
 DisplayWindow::makeCurrent() () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqpa-mirserver.so
 MirOpenGLContext::makeCurrent(QPlatformSurface*) () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqpa-mirserver.so
 QOpenGLContext::makeCurrent(QSurface*) () from /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
 ?? () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
 ?? () from /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
Title: unity8 crashed with SIGSEGV in DisplayWindow::makeCurrent()
UpgradeStatus: Upgraded to vivid on 2014-10-20 (85 days ago)
UserGroups: adm autopilot cdrom dip lpadmin plugdev sambashare sudo vboxusers

[Apport retracing service (apport)]

StacktraceTop:
 QHash<int, QWindowSystemInterface::TouchPoint>::remove (this=0x7fb00d45bcd0, akey=<optimized out>) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qhash.h:826
 ?? ()
 ?? ()
 QOpenGLContext::makeCurrent (this=0x7fb00d45bd00, surface=0x7fb06a6feafb <SessionAuthorizer::connection_is_allowed(mir::frontend::SessionCredentials const&)+683>) at kernel/qopenglcontext.cpp:813
 QSGRenderThread::sync (this=0x1df55d0) at scenegraph/qsgthreadedrenderloop.cpp:537

[Gerry Boland (gerboland)]

Top frame of LP's backtrace rubbish. I got the following:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fb6d7051700 (LWP 3053)]
0x00007fb73bf9c463 in DisplayWindow::makeCurrent() () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqpa-mirserver.so
(gdb) bt
#0 0x00007fb73bf9c463 in DisplayWindow::makeCurrent() () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqpa-mirserver.so
#1 0x00007fb73bf9ec07 in MirOpenGLContext::makeCurrent(QPlatformSurface*) () from /usr/lib/x86_64-linux-gnu/qt5/plugins/platforms/libqpa-mirserver.so
#2 0x00007fb7456555c2 in QOpenGLContext::makeCurrent (this=0x10a92a0, surface=0xce9960) at kernel/qopenglcontext.cpp:813
#3 0x00007fb744abfb12 in QSGRenderThread::sync (this=0x131bc90) at scenegraph/qsgthreadedrenderloop.cpp:537
#4 0x00007fb744abfe98 in QSGRenderThread::syncAndRender (this=0x131bc90) at scenegraph/qsgthreadedrenderloop.cpp:587
#5 0x00007fb744ac07d8 in QSGRenderThread::run (this=0x131bc90) at scenegraph/qsgthreadedrenderloop.cpp:704
#6 0x00007fb743b3dd2e in QThreadPrivate::start (arg=0x131bc90) at thread/qthread_unix.cpp:345
#7 0x00007fb7423690a5 in start_thread (arg=0x7fb6d7051700) at pthread_create.c:309
#8 0x00007fb7432b190d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

and the unity8 log shows me:

QtCompositor::setAllWindowsExposed false
DisplayWindow::event got QEvent::Hide
QtCompositor::setAllWindowsExposed true
DisplayWindow::event got QEvent::Show

So appears as if Qt is trying to render with the display off - which will crash.

[Gerry Boland (gerboland)]

A little more digging: bringing up mir_proving_server and xeyes manually:
1. sudo stop lightdm
2. sudo mir_proving_server
3. sudo chown $USER /tmp/mir_socket
4. sudo chmod 777 /tmp/mir_socket
5. Xmir :1 -mirSocket /tmp/mir_socket
6. in separate shell, do:
DISPLAY=:1 xeyes

I can tell X to blank the display with
DISPLAY=:1 xset dpms force off
and Mir deals with it ok - no crash.

[Daniel van Vugt (vanvugt)]

The stack traces are a little confused as always by the fact that QtMir names some of its things "Mir*" while not being a part of Mir. There doesn't seem to be any Mir code in the stack traces.

That and the same bug doesn't exist in the mir_proving_server.

[Christopher Townsend (townsend)]

This doesn't seem to occur anymore. Not sure what fixed it, so I'm just going to close Invalid.