gnome-shell crashed with SIGSEGV in meta_monitor_mode_get_resolution → calculate_scale → meta_monitor_calculate_mode_scale → calculate_monitor_scale → derive_calculated_global_scale

StacktraceTop:
 meta_monitor_mode_get_resolution (monitor_mode=monitor_mode@entry=0x0, width=width@entry=0x7ffceb5a36f8, height=height@entry=0x7ffceb5a36fc) at backends/meta-monitor.c:1582
 calculate_scale (monitor_mode=0x0, monitor=0x55d2cc3cb100) at backends/meta-monitor.c:1377
 meta_monitor_calculate_mode_scale (monitor=0x55d2cc3cb100, monitor_mode=0x0) at backends/meta-monitor.c:1439
 calculate_monitor_scale (monitor=0x55d2cc3cb100, manager=0x7fadfc014ae0) at backends/meta-monitor-manager.c:174
 derive_calculated_global_scale (manager=0x7fadfc014ae0) at backends/meta-monitor-manager.c:188

bug #1723620 is actually the original error that killed my session. I belatedly noticed that *this* one, that was popped up for me next time I logged in, was the error that occurred in gdm's gnome-shell about 18 minutes later. Both still occurred while I was away from the computer.

Status changed to 'Confirmed' because the bug affects multiple users.

Of interest - this happens to me, also on a 4k screen using DisplayPort 1.2

There was a Nvidia driver released today 384.94: https://devtalk.nvidia.com/default/topic/1025953/b/t/post/5217907/#5217907

In the notes they mention:
* Fixed a bug that could cause OpenGL applications to crash after a prolonged DPMS sleep state on a monitor driven with PRIME Sync.

Can you upgrade to this version and see if that resolves the issue?

In fact I'm already on 387.22 which, I see from a nearby post on the same forum, has the same fix: https://devtalk.nvidia.com/default/topic/1025794/unix-graphics-announcements-and-news/linux-solaris-and-freebsd-driver-387-22/

It hasn't helped.

TBH I don't think it applies as (fx: me reading up more on what PRIME sync is) I don't think I'm using PRIME sync... my mobo has integrated Intel HD4600 as well but I don't use it at all, and the nvidia card is selected as default in uefi bios. I've done no prime sync setup at all.

There appear to be a shedload of upstream gnome-shell bugs relating to these problems, and not everyone having them is using nVidia, though it may be that they are all using DisplayPort to connect to their monitors, although why something as user-level as gnome-shell is bothered with *which* ports are used is beyond me...

Also tracking in:
https://errors.ubuntu.com/problem/84e05b052e88b79520a684d6113084e9be8bc339

This is now fixed as per https://gitlab.gnome.org/GNOME/mutter/commit/1b439c42d1b0d9d53abe6b9052f26d3b355b57d4 that I've already cherry-picked on mutter 3.28 branch, so it will be added on next point-release.

Upstream bug:
https://gitlab.gnome.org/GNOME/mutter/issues/130

Fixed in mutter 3.29.1 and 3.28.2

mutter (3.28.2-2) unstable; urgency=medium

  * Team upload
  * d/p/frames-Handle-touch-events.patch,
    d/p/frames-Make-1st-button-motion-handlers-take-generic-event.patch:
    Drop cherry-picked patches that caused a regression (Closes: #899181)

 -- Simon McVittie <email address hidden> Sun, 20 May 2018 15:21:35 +0100

^^^
Fix released in 18.10 only right now. Not 18.04.

The fix for this is in proposed and included in https://launchpad.net/ubuntu/+source/mutter/3.28.2-2~ubuntu18.04.1

It looks like we're still seeing some crash for this, I've doing some more debugging at https://gitlab.gnome.org/GNOME/mutter/issues/130#note_278690

This bug was fixed in the package mutter - 3.28.3-2

---------------
mutter (3.28.3-2) unstable; urgency=medium

  * Team upload

  [ Iain Lane ]
  * debian/gbp.conf: Set the upstream branch to upstream/3.28.x, since we've
    branched for experimental now.

  [ Marco Trevisan (Treviño) ]
  * d/p/native-gpu-Handle-drmModeSetCrtc-failing-gracefully.patch:
    - Avoid crashing when warning about wrongly set crtc mode
      (LP: #1754949)
  * d/p/gpu-kms-Don-t-crash-if-drmModeGetResources-returns-N.patch:
    - Don't crash if drmModeGetResources returns NULL (LP: #1767956)
  * d/p/window-wayland-Always-update-monitor-for-non-user-ops.patch:
    - Always update monitor in wayland, avoiding crash (LP: #1784398)
  * d/p/monitor-manager-Filter-out-low-screen-resolutions.patch:
    - Don't return screen resolutions that can't be applied (LP: #1772831)
  * d/p/window-Don-t-refuse-to-move-focus-to-the-grab-window.patch,
    d/p/window-Explicitly-exclude-unmanaging-window-from-focus-ag.patch:
    - Don't crash if a modal dialog closes while being dragged
      (LP: #1422253)
  * d/p/monitor-Use-current-monitor-mode-to-check-whether-active.patch:
    - Don't try to use an invalid monitor mode to figure out scaling
      (LP: #1723615)

  [ Simon McVittie ]
  * Sort patch series in upstream order, with patches applied upstream
    first
  * d/copyright: Remove obsolete FSF postal addresses
  * Standards-Version: 4.1.5 (no changes required)
  * Set Rules-Requires-Root to no
  * Update symbols file

 -- Simon McVittie <email address hidden> Tue, 31 Jul 2018 15:35:03 +0100

FWIW I can't reproduce this any more either; since 18.04 in fact I've had no problems with gnome-shell crashing. The monitor very nearly always does wake up when it's supposed to now (some difference in the dpms signal being sent? Previously it would always wake for windows and just had a hard time with Linux), and on the few occasions it hasn't, I haven't lost my session and I just needed to powercycle the monitor properly. So I was under the impression this was all fixed. :-) Possibly by not-obviously-related changes elsewhere.

Thanks for the feedback Rachel,

Although we still got some automatic reports about this happening, so a proper fix for this is included in mutter 3.29.90-1

Sure, just thought I'd better say something as it was my report originally. :-)

Hello Rachel, or anyone else affected,

Accepted mutter into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/mutter/3.28.3-2~ubuntu18.04.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

I don't get any mentioned regression with mutter 3.28.3-2~ubuntu18.04.1, while no more reports for this crash are present for such version in e.u.c, thus I mark this as verified.

This bug was fixed in the package mutter - 3.28.3-2~ubuntu18.04.1

---------------
mutter (3.28.3-2~ubuntu18.04.1) bionic; urgency=medium

  * No-change backport from unstable to bionic

mutter (3.28.3-2) unstable; urgency=medium

  * Team upload

  [ Iain Lane ]
  * debian/gbp.conf: Set the upstream branch to upstream/3.28.x, since we've
    branched for experimental now.

  [ Marco Trevisan (Treviño) ]
  * d/p/native-gpu-Handle-drmModeSetCrtc-failing-gracefully.patch:
    - Avoid crashing when warning about wrongly set crtc mode
      (LP: #1754949)
  * d/p/gpu-kms-Don-t-crash-if-drmModeGetResources-returns-N.patch:
    - Don't crash if drmModeGetResources returns NULL (LP: #1767956)
  * d/p/window-wayland-Always-update-monitor-for-non-user-ops.patch:
    - Always update monitor in wayland, avoiding crash (LP: #1784398)
  * d/p/monitor-manager-Filter-out-low-screen-resolutions.patch:
    - Don't return screen resolutions that can't be applied (LP: #1772831)
  * d/p/window-Don-t-refuse-to-move-focus-to-the-grab-window.patch,
    d/p/window-Explicitly-exclude-unmanaging-window-from-focus-ag.patch:
    - Don't crash if a modal dialog closes while being dragged
      (LP: #1422253)
  * d/p/monitor-Use-current-monitor-mode-to-check-whether-active.patch:
    - Don't try to use an invalid monitor mode to figure out scaling
      (LP: #1723615)

  [ Simon McVittie ]
  * Sort patch series in upstream order, with patches applied upstream
    first
  * d/copyright: Remove obsolete FSF postal addresses
  * Standards-Version: 4.1.5 (no changes required)
  * Set Rules-Requires-Root to no
  * Update symbols file

mutter (3.28.3-1~ubuntu18.04.1) bionic; urgency=medium

  * No-change backport to bionic (LP: #1783311)

mutter (3.28.3-1) unstable; urgency=medium

  * New upstream release
  * d/p/backends-Add-logical-monitor-monitor-output-crtc-ref-chai.patch,
    d/p/backends-Move-MetaOutput-crtc-field-into-private-struct.patch,
    d/p/clutter-device-evdev-Get-devices-from-main-seat-if-no-rea.patch,
    d/p/clutter-evdev-Don-t-ignore-CAPS-lock-as-modifier.patch,
    d/p/clutter-evdev-ignore-injected-events-from-IM.patch,
    d/p/clutter-seat-evdev-Add-function-to-get-device-by-id.patch,
    d/p/device-manager-evdev-Add-main-seat-to-seats-by-default.patch,
    d/p/device-manager-evdev-Free-the-main-seat-on-finalize.patch,
    d/p/device-manager-evdev-Set-and-unset-the-stage-for-the-main.patch,
    d/p/frames-Allow-for-unknown-mouse-buttons.patch,
    d/p/frames-Handle-touch-events.patch,
    d/p/frames-Make-1st-button-motion-handlers-take-generic-event.patch,
    d/p/renderer-native-Don-t-crash-if-the-FB-surface-can-t-be-lo.patch,
    d/p/wayland-Compare-geometries-after-chaining-up.patch,
    d/p/wayland-Don-t-reset-input-focus-on-text-commit.patch,
    d/p/wayland-Use-cursor-position-in-logical-monitor.patch,
    d/p/wayland-update-enter-leave-output-after-effects.patch,
    d/p/window-actor-add-new-signal-effects-completed.patch:
    Remove patches already applied on 3.28 branch

 -- Marco Trevisan (Treviño) <email address hidden> Fri, 03 Aug 2018 05:20:10 +0100

The verification of the Stable Release Update for mutter has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.