The nouveau isn't threadsafe and the Qt renderer uses threaded GL by default.
We don't know if Mir's default renderer would also exhibit the same issue when running multimonitor. (The Mir renderer uses a thread per monitor, but this is a simpler usage pattern than Qt and may not manifest problems.) ** Changed in: mir Status: Triaged => Incomplete ** Changed in: mir Importance: High => Undecided ** Changed in: mir (Ubuntu) Status: Triaged => Incomplete ** Changed in: mir (Ubuntu) Importance: High => Undecided ** Changed in: canonical-devices-system-image Assignee: Stephen M. Webb (bregma) => (unassigned) -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to mesa in Ubuntu. https://bugs.launchpad.net/bugs/1553328 Title: Mir/Unity8/USC crashes/freezes on nouveau (nv50) in pushbuf_kref() especially with multiple monitors, webbrowser-app or system settings Status in Canonical System Image: Triaged Status in Mir: Incomplete Status in Nouveau Xorg driver: Unknown Status in Unity System Compositor: Triaged Status in libdrm package in Ubuntu: Triaged Status in mesa package in Ubuntu: Invalid Status in mir package in Ubuntu: Incomplete Status in qtmir package in Ubuntu: In Progress Status in qtubuntu package in Ubuntu: In Progress Bug description: Unit8 froze up while I was trying to open system settings. ProblemType: Crash DistroRelease: Ubuntu 16.04 Package: unity8 8.11+16.04.20160216.1-0ubuntu1 ProcVersionSignature: Ubuntu 4.4.0-9.24-generic 4.4.3 Uname: Linux 4.4.0-9-generic x86_64 ApportVersion: 2.20-0ubuntu3 Architecture: amd64 Date: Fri Mar 4 19:12:54 2016 ExecutablePath: /usr/bin/unity8 InstallationDate: Installed on 2015-05-10 (299 days ago) InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422) ProcCmdline: unity8 SegvAnalysis: Segfault happened at: 0x7f58d568706c: mov 0x8(%rsi),%edx PC (0x7f58d568706c) ok source "0x8(%rsi)" (0x00000008) not located in a known VMA region (needed readable region)! destination "%edx" ok Stack memory exhausted (SP below stack segment) SegvReason: reading NULL VMA Signal: 11 SourcePackage: unity8 StacktraceTop: ?? () from /usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2 ?? () from /usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2 ?? () from /usr/lib/x86_64-linux-gnu/dri/nouveau_dri.so ?? () from /usr/lib/x86_64-linux-gnu/dri/nouveau_dri.so ?? () from /usr/lib/x86_64-linux-gnu/mesa-egl/libEGL.so.1 Title: unity8 crashed with SIGSEGV UpgradeStatus: Upgraded to xenial on 2015-11-07 (118 days ago) UserGroups: adm autopilot cdrom dip lpadmin plugdev sambashare sudo To manage notifications about this bug go to: https://bugs.launchpad.net/canonical-devices-system-image/+bug/1553328/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp