Created attachment 131659 [details]
Screenshot - corrupted childwindow

Opening child windows in the GUI of writer, calc, impress or draw results in a corrupted child window.

OS: Suse Tumbleweed 
Graphics: AMD A10 with OSS graphics drivers
MESA: 17.0.0
Window Manager: kde plasma / kwin 5.9.1

How to reproduce (can always be reproduced but it seems to need the symbol child window to trigger) :
* Start writer, calc, impress or draw
* Select "Insert->Symbol"
  If that works select "Extra->Options" 
  If that still works select "Insert->Symbol" multiple times
* At some point the screen start flickering and the desktop becomes unusable
* In KDE I can go to the top-left corner of the desktop to show all applications on the desktop -> That still works and I see the new child-window which was supposed to open as a garbeled picture. 
* In the Xorg.0.log I get hundreds of the following errors:

2017-03-05T21:24:10.686432+01:00 athlon kernel: [32203.426452] radeon 0000:00:01.0: evergreen_surface_check_linear_aligned:216 texture pitch 840 invalid must be aligned with 64
2017-03-05T21:24:10.686474+01:00 athlon kernel: [32203.426456] radeon 0000:00:01.0: evergreen_cs_track_validate_texture:831 texture invalid 0x0d1c1a01 0x1000024c 0x0a0a0000 0x00000000 0x00000000 0x8002001a
2017-03-05T21:24:10.686481+01:00 athlon kernel: [32203.426497] [drm:radeon_cs_ioctl [radeon]] *ERROR* Invalid command stream !

* After closing the the corrupted childwindow everything works again normally.


See screen shots of corrupted window attached .