Public bug reported: ProblemType: Crash Architecture: amd64 Date: Mon Oct 12 19:17:11 2026 DistroRelease: Ubuntu 26.04 ExecutablePath: /usr/bin/compiz Package: compiz-core 1:0.9.14.2+25.10.20250930-0ubuntu3 PackageArchitecture: amd64 ProcCmdline: /usr/bin/compiz Signal: 11 SignalName: SIGSEGV SourcePackage: compiz UpgradeStatus: Upgraded to resolute on 2026-06-27 (107 days ago) StacktraceTop: unity::ui::IconRenderer::PreprocessIcons(std::__cxx11::list<unity::ui::RenderArg, std::allocator<unity::ui::RenderArg> >&, nux::Rect const&) () from /usr/lib/x86_64-linux-gnu/compiz/libunityshell.so unity::ui::UnityWindowView::Draw(nux::GraphicsEngine&, bool) () from /usr/lib/x86_64-linux-gnu/compiz/libunityshell.so nux::View::ProcessDraw(nux::GraphicsEngine&, bool) () from /usr/lib/x86_64-linux-gnu/libnux-4.0.so.0 nux::Layout::ProcessDraw(nux::GraphicsEngine&, bool) () from /usr/lib/x86_64-linux-gnu/libnux-4.0.so.0 nux::BaseWindow::DrawContent(nux::GraphicsEngine&, bool) () from /usr/lib/x86_64-linux-gnu/libnux-4.0.so.0 Tags: resolute ubuntu
# Unity Alt-Tab crash — upstream bug report (draft for Launchpad) ## Where to file - Project: Ubuntu - Package: unity (libunityshell.so ships in `unity`, not compiz-core) - URL: https://bugs.launchpad.net/ubuntu/+source/unity/+filebug - Or from a terminal: `ubuntu-bug unity` (auto-attaches this crash file + system info) ## Suggested title compiz crashes with SIGSEGV in unityshell IconRenderer::PreprocessIcons during Alt-Tab switcher draw ## Summary Pressing Alt-Tab crashes compiz with SIGSEGV inside libunityshell.so while drawing the Alt-Tab window switcher. Reproduces on a fresh OS install with default Unity session — so it is not caused by user config. ## Steps to reproduce 1. Fresh Ubuntu 26.04 (resolute) install, default Unity session. 2. Open 2+ windows. 3. Press Alt-Tab. -> compiz segfaults, session restarts. ## Actual result SIGSEGV in unity::ui::IconRenderer::PreprocessIcons (libunityshell.so). ## Expected result Alt-Tab switcher renders; no crash. ## Backtrace (top frames, from /var/crash/_usr_bin_compiz.1000.crash) ProblemType: Crash Signal: 11 (SIGSEGV) ExecutablePath: /usr/bin/compiz ProcCmdline: /usr/bin/compiz Package: compiz-core 1:0.9.14.2+25.10.20250930-0ubuntu3 SourcePackage: compiz DistroRelease: Ubuntu 26.04 Architecture: amd64 UpgradeStatus: Upgraded to resolute on 2026-06-27 StacktraceTop: unity::ui::IconRenderer::PreprocessIcons(std::list<unity::ui::RenderArg>&, nux::Rect const&) from /usr/lib/x86_64-linux-gnu/compiz/libunityshell.so unity::ui::UnityWindowView::Draw(nux::GraphicsEngine&, bool) from /usr/lib/x86_64-linux-gnu/compiz/libunityshell.so nux::View::ProcessDraw(nux::GraphicsEngine&, bool) from libnux-4.0.so.0 nux::Layout::ProcessDraw(...) from libnux-4.0.so.0 nux::BaseWindow::DrawContent(...) from libnux-4.0.so.0 The crashing frame is UnityWindowView::Draw -> IconRenderer::PreprocessIcons, i.e. the Alt-Tab switcher rendering its window icons. unitymtgrabhandles is NOT in the crash path; removing it does not help. ## Environment - Ubuntu 26.04 (resolute), upgraded 2026-06-27, kernel 7.2.6-070206-generic - compiz 1:0.9.14.2+25.10.20250930-0ubuntu3, unity package provides libunityshell.so - GPU: AMD Radeon RX 6800 XT (radeonsi, navi21, ACO, DRM 3.64), 16GB - GL: OpenGL 4.6 Core, Mesa 26.0.8-1ubuntu0.3, Accelerated: yes - Reproduces on fresh install (config-independent) ## History / timeline - Earliest Alt-Tab crash diagnostics on this host: 2026-06-28. - System upgraded to resolute (Ubuntu 26.04) 2026-06-27 (UpgradeStatus in the crash report). The crash appeared within ~1 day of the distro upgrade and has recurred continuously for the ~107 days since — across many sessions and reboots. - This is NOT the separate known compiz startup hang (hung `unity_support_test -p`, 0% CPU / poll_schedule_timeout, which shows up as compiz crash-loop at login). This report is specifically the Alt-Tab-triggered SIGSEGV in unityshell's switcher icon renderer, which is a different code path. - Separate note for triage: this host also experiences Mesa/RADV compositing flicker (GTT_WC workqueue) on the same RX 6800 XT. Reporter has asked to keep that out of this report for now; it is a distinct symptom and not claimed to be related. ## Notes - No config workaround: disabling scale/expo/ezoom/animation and unitymtgrabhandles does not stop the crash — the segfault is in unityshell's switcher icon preprocessor itself. - Only one compiz version is available in the archive (no downgrade candidate). ## Disclaimer This report was prepared with the assistance of an AI agent (Hermes Agent) at the user's request; the backtrace and system data above are taken directly from the local apport crash file and are unmodified. ** Affects: unity (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2170564 Title: compiz crashes with SIGSEGV in unityshell IconRenderer::PreprocessIcons during Alt-Tab switcher draw To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/2170564/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
