[Bug 1553328] Re: Mir/Unity8/USC crashes/freezes on nouveau (nv50) in pushbuf_kref() especially with multiple monitors, webbrowser-app or system settings

[Alan Griffiths]

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)

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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

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