Xorg assert failure: Xorg: ../../nouveau/pushbuf.c:238: pushbuf_krel: Assertion `bkref' failed.

[Oleksandr Pikozh]

I have three options for my video adapter: nvidia-304 (+ nvidia-opencl-icd-304 and nvidia-settings) and xserver-xorg-video-nouveau. If I uninstall both of them (I was forced to do that because xserver-xorg-video-nouveau doesn't work at all and nvidia-304 doesn't work at latest version), system seems to work, but periodically (5 minutes to 1 hour) XOrg crashes.

Crashes seem to occur at random points of time (unrelated to my actions), but persistently.

1) lsb_release -rd
Description: Ubuntu 16.04.1 LTS
Release: 16.04

2) apt-cache policy xorg xserver-xorg-core
xorg:
  Installed: 1:7.7+13ubuntu3
  Candidate: 1:7.7+13ubuntu3
  Version table:
 *** 1:7.7+13ubuntu3 500
        500 http://ua.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status
xserver-xorg-core:
  Installed: 2:1.18.4-0ubuntu0.1
  Candidate: 2:1.18.4-0ubuntu0.1
  Version table:
 *** 2:1.18.4-0ubuntu0.1 500
        500 http://ua.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2:1.18.3-1ubuntu2 500
        500 http://ua.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

3) I expected XOrg to run stably (or not to run at all if some critical components are missing).

4) It crashes every 5min-1hour.

ProblemType: Crash
DistroRelease: Ubuntu 16.04
Package: xserver-xorg-core 2:1.18.4-0ubuntu0.1
ProcVersionSignature: Ubuntu 4.4.0-45.66-generic 4.4.21
Uname: Linux 4.4.0-45-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
AssertionMessage: Xorg: ../../nouveau/pushbuf.c:238: pushbuf_krel: Assertion `bkref' failed.
Date: Wed Nov 9 13:20:43 2016
ExecutablePath: /usr/lib/xorg/Xorg
ExecutableTimestamp: 1473867446
InstallationDate: Installed on 2015-11-10 (364 days ago)
InstallationMedia: Kubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20151110)
ProcCmdline: /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{0f1dcf2c-924d-493a-b72a-0d3865f108e8} -background none -noreset -displayfd 17 vt7
ProcCwd: /
Signal: 6
SourcePackage: xorg-server
StacktraceTop:
 __assert_fail_base (fmt=<optimized out>, assertion=assertion@entry=0x7fd94a537728 "bkref", file=file@entry=0x7fd94a53770a "../../nouveau/pushbuf.c", line=line@entry=238, function=function@entry=0x7fd94a537768 "pushbuf_krel") at assert.c:92
 __GI___assert_fail (assertion=0x7fd94a537728 "bkref", file=0x7fd94a53770a "../../nouveau/pushbuf.c", line=238, function=0x7fd94a537768 "pushbuf_krel") at assert.c:101
 ?? () from /usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2
 nouveau_pushbuf_reloc () from /usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2
 ?? () from /usr/lib/x86_64-linux-gnu/dri/nouveau_dri.so
Title: Xorg assert failure: Xorg: ../../nouveau/pushbuf.c:238: pushbuf_krel: Assertion `bkref' failed.
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

[Apport retracing service (apport)]

StacktraceTop:
 __assert_fail_base (fmt=<optimized out>, assertion=assertion@entry=0x7fd94a537728 "bkref", file=file@entry=0x7fd94a53770a "../../nouveau/pushbuf.c", line=line@entry=238, function=function@entry=0x7fd94a537768 <__PRETTY_FUNCTION__.6215> "pushbuf_krel") at assert.c:92
 __GI___assert_fail (assertion=0x7fd94a537728 "bkref", file=0x7fd94a53770a "../../nouveau/pushbuf.c", line=238, function=0x7fd94a537768 <__PRETTY_FUNCTION__.6215> "pushbuf_krel") at assert.c:101
 pushbuf_krel () from /tmp/apport_sandbox_HhoZdt/usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2
 nouveau_pushbuf_reloc () from /tmp/apport_sandbox_HhoZdt/usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2
 PUSH_RELOC (tor=0, vor=0, flags=4096, offset=0, bo=<optimized out>, push=0x563469a72df0) at ../../../../../src/gallium/drivers/nouveau/nv30/nv30_winsys.h:26

[Daniel van Vugt (vanvugt)]

The crash is occurring in libdrm_nouveau.so.2 which comes from source package `libdrm'. So it seems to be just a nouveau driver crash and not a general Xorg issue.

[Oleksandr Pikozh (o-pikozh)]

apt-cache policy libdrm-nouveau2
libdrm-nouveau2:
  Installed: 2.4.67-1ubuntu0.16.04.2
  Candidate: 2.4.67-1ubuntu0.16.04.2
  Version table:
 *** 2.4.67-1ubuntu0.16.04.2 500
        500 http://ua.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     2.4.67-1 500
        500 http://ua.archive.ubuntu.com/ubuntu xenial/main amd64 Packages

Some other info needed?