[Bug 1776447] Re: Xorg's Indirect GLX broken from upstream regression

Thu Jan 30 19:11:27 UTC 2020

both changes are now in upstream Xorg's repository, as PR388 was merged
a few hours ago. So the changes in this debdiff are a backport of those
to Bionic, Eoan and Focal (although if Focal were to sync with the
upstream code then the delta won't be necessary going forward).

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https://bugs.launchpad.net/bugs/1776447

Title:
  Xorg's Indirect GLX broken from upstream regression

Status in X.Org X server:
  Fix Released
Status in xorg-server package in Ubuntu:
  Triaged

Bug description:
  [Impact]

   * IGLX is a way for an opengl application sending the 3D drawing GLX
  commands to the Xorg server for rendering instead of using the DRI
  infrastructure it is commonplace for High Performance Compute and
  Scientific institutions to use this feature of the Xorg server. (ref:
  https://www.phoronix.com/scan.php?page=news_item&px=Xorg-IGLX-
  Potential-Bye-Bye)

   * The feature is completely broken, currently, and any attempt to use
  it will cause the Xorg server to crash. This feature has been broken
  since a commit upstream in 2016.

   * The attached patch is from the revert commit entered into the
  upstream repository on 28 Jan 2020 following a git bisect of the bug
  discovering the offending commit.

  [Test Case]

   * Create a new file at /etc/X11/xorg.conf.d/99-IGLX.conf with the
  following contents:

  ```
  Section "ServerFlags"
      Option "IndirectGLX" "on"
  EndSection
  ```

   * Log out of your Xorg session
   * Switch to a VT (Ctrl+Alt+F2) and login
   * Run `sudo systemctl restart gdm` to restart Xorg
   * Login to the graphical session
   * If you do not have mesa-utils installed, then install it with the terminal command `sudo apt install mesa-utils`
   * Open a terminal and execute `LIBGL_ALWAYS_INDIRECT=1 glxgears`
   * If the fix is successful then glxgears should start and remain active without the Xorg server or glxgears crashing/segfaulting

  [Regression Potential]

   * This change is within DRI-related functionality and so might break
  all 3D accelerated applications.

   * There is a potential that the change is insufficient to fix the
  IGLX feature and so attempts to use it may still have undesirable and
  undefined results.

   * Upstream has run the patch through their CI system, which passed
  with no errors. This does not necessarily mean the patch will achieve
  the desired results, but at least indicates that the code does compile
  cleanly and can start an Xvfb headless instance.

  [Other Info]

   * This bug affects Ubuntu releases all the way back to, and
  including, Bionic 18.04.

  ---- Original Bug Report Follows ----

  There's already an upstream bug report here:

  https://bugs.freedesktop.org/show_bug.cgi?id=99555

  Basically, with Option "IndirectGLX" "True" and
  LIBGL_ALWAYS_INDIRECT=1 I get immediate crashes e.g. with glxgear:

  steved at xubuntu:~$ LIBGL_ALWAYS_INDIRECT=true glxgears
  Running synchronized to the vertical refresh.  The framerate should be
  approximately the same as the monitor refresh rate.
  X Error of failed request:  255
    Major opcode of failed request:  155 (GLX)
    Minor opcode of failed request:  1 (X_GLXRender)
    Serial number of failed request:  42
    Current serial number in output stream:  936

  I am trying to run what is effectively a traditional X Terminal, but
  as the hardware I am using has a 3D accelerated chipset it seems
  sensible to try to use it..

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: xserver-xorg-core 2:1.19.6-1ubuntu4
  ProcVersionSignature: Ubuntu 4.15.0-22.24-generic 4.15.17
  Uname: Linux 4.15.0-22-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7.1
  Architecture: amd64
  BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
  Date: Tue Jun 12 10:09:30 2018
  DistUpgraded: Fresh install
  DistroCodename: bionic
  DistroVariant: ubuntu
  DkmsStatus:
   rtl8812au, 4.3.8.12175.20140902+dfsg, 4.15.0-22-generic, x86_64: installed
   rtl8812au, 4.3.8.12175.20140902+dfsg, 4.15.0-23-generic, x86_64: installed
  ExtraDebuggingInterest: Yes
  GraphicsCard:
   Intel Corporation Device [8086:5a85] (rev 0b) (prog-if 00 [VGA controller])
     Subsystem: Intel Corporation Device [8086:2212]
  InstallationDate: Installed on 2018-05-31 (11 days ago)
  InstallationMedia: Xubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
  MachineType: AZW S I
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-22-generic root=/dev/mapper/xubuntu--vg-root ro noresume
  SourcePackage: xorg-server
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 12/18/2017
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: 00.12
  dmi.board.asset.tag: Default string
  dmi.board.name: AB1
  dmi.board.vendor: IP3 Tech
  dmi.board.version: Default string
  dmi.chassis.asset.tag: Default string
  dmi.chassis.type: 35
  dmi.chassis.vendor: Default string
  dmi.chassis.version: Default string
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr00.12:bd12/18/2017:svnAZW:pnSI:pvrDefaultstring:rvnIP3Tech:rnAB1:rvrDefaultstring:cvnDefaultstring:ct35:cvrDefaultstring:
  dmi.product.family: Mini PC
  dmi.product.name: S I
  dmi.product.version: Default string
  dmi.sys.vendor: AZW
  version.compiz: compiz N/A
  version.libdrm2: libdrm2 2.4.91-2
  version.libgl1-mesa-dri: libgl1-mesa-dri 18.0.0~rc5-1ubuntu1
  version.libgl1-mesa-glx: libgl1-mesa-glx 18.0.0~rc5-1ubuntu1
  version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4
  version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
  version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
  version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
  version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2

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