Segmentation fault when starting a second xserver inside an xserver session Driver 355.11 (EVO Push

Hi

I try to start a new Xserver session inside of an already running Xserver (runs KDE5). When i do this, the Nvidia driver crashes.

manuel@orion ~ $ xinit /usr/bin/xterm -- :1 "vt${XDG_VTNR}"

X.Org X Server 1.16.4
Release Date: 2014-12-20
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.19.0-15-generic x86_64 Gentoo
Current Operating System: Linux orion 4.0.5-gentoo #1 SMP PREEMPT Fri Sep 4 02:15:52 CEST 2015 x86_64
Kernel command line: BOOT_IMAGE=/vmlinuz-4.0.5-gentoo root=/dev/sda3 ro init=/usr/lib/systemd/systemd
Build Date: 04 September 2015  10:36:57AM
 
Current version of pixman: 0.32.6
        Before reporting problems, check http://wiki.x.org
        to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
        (++) from command line, (!!) notice, (II) informational,
        (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.1.log", Time: Wed Sep 23 12:12:45 2015
(==) Using config directory: "/etc/X11/xorg.conf.d"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
(EE) 
(EE) Backtrace:
(EE) 0: X (xorg_backtrace+0x42) [0x590fe2]
(EE) 1: X (0x400000+0x195109) [0x595109]
(EE) 2: /lib64/libc.so.6 (0x7f52099d6000+0x34ef0) [0x7f5209a0aef0]
(EE) 3: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xef524) [0x7f52049b1524]
(EE) 4: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xe2092) [0x7f52049a4092]
(EE) 5: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xe3c80) [0x7f52049a5c80]
(EE) 6: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xfd8da) [0x7f52049bf8da]
(EE) 7: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xfddc4) [0x7f52049bfdc4]
(EE) 8: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xe325c) [0x7f52049a525c]
(EE) 9: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xe345a) [0x7f52049a545a]
(EE) 10: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xe3a8b) [0x7f52049a5a8b]
(EE) 11: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xd2bef) [0x7f5204994bef]
(EE) 12: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xd23c8) [0x7f52049943c8]
(EE) 13: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xcfacb) [0x7f5204991acb]
(EE) 14: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xd113b) [0x7f520499313b]
(EE) 15: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0x65c52) [0x7f5204927c52]
(EE) 16: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xb2189) [0x7f5204974189]
(EE) 17: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xb21de) [0x7f52049741de]
(EE) 18: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0xb44fa) [0x7f52049764fa]
(EE) 19: /usr/lib64/xorg/modules/drivers/nvidia_drv.so (0x7f52048c2000+0x56bdde) [0x7f5204e2ddde]
(EE) 
(EE) Segmentation fault at address 0x20
(EE) 
Fatal server error:
(EE) Caught signal 11 (Segmentation fault). Server aborting
(EE) 
(EE) 
Please consult the The X.Org Foundation support 
         at http://wiki.x.org
 for help. 
(EE) Please also check the log file at "/var/log/Xorg.1.log" for additional information.
(EE) 
(EE) Server terminated with error (1). Closing log file.
^C^Cxinit: giving up
xinit: unable to connect to X server: Interrupted system call
xinit: unexpected signal 2
manuel@orion ~ $

In the Xorg log is the following:

[   895.362] (II) NVIDIA: Allocated GPU:0 (GPU-3d336a7e-dc77-cb0d-5d1d-7f81a9a27ecc) @
[   895.362] (II) NVIDIA:     PCI:0000:01:00.0
[   895.386] (EE) NVIDIA: GPU:0: EVO Push buffer channel allocation failed
[   895.387] (EE) NVIDIA: GPU:0: Failed to allocate EVO core DMA push buffer
[   895.388] (EE)
[   895.388] (EE) Backtrace:

/etc/X11/xorg.conf.d/nvidia.conf

Section "Device"
   Identifier  "nvidia"
   Driver      "nvidia"
   Option "UseDPLib" "false"
   Option         "ProbeAllGpus"          "false"
 EndSection

I googled for the EVO Error and unfortunatelly the workarounds ( Option “UseDPLib” “false”
and/or Option “ProbeAllGpus” “false”) in the config do not work :-(

I use a GTX 750ti and the newest driver but im sure you get that from your Bugreport script…

What other info do you need to track this bug down ?

Thanks
nvidia-bug-report.log.gz (78.8 KB)
Xorg.1.log (8.27 KB)
Xorg.0.log (65.8 KB)