Comment 18 for bug 617201

6:13.1-1ubuntu2 works fine for me.
With 6:13.1-1ubuntu4 I have this crash right after logon:

[ 4947.741]
Backtrace:
[ 4947.741] 0: /usr/bin/X (xorg_backtrace+0x28) [0x462758]
[ 4947.742] 1: /usr/bin/X (0x400000+0x5d87d) [0x45d87d]
[ 4947.742] 2: /lib/libpthread.so.0 (0x7f3952268000+0xfb40) [0x7f3952277b40]
[ 4947.742] 3: /usr/lib/xorg/modules/drivers/radeon_drv.so (0x7f394f12a000+0xd70b4) [0x7f394f2010b4]
[ 4947.742] 4: /lib/libdrm.so.2 (drmHandleEvent+0x103) [0x7f394f841533]
[ 4947.742] 5: /usr/bin/X (WakeupHandler+0x4b) [0x43f7bb]
[ 4947.742] 6: /usr/bin/X (WaitForSomething+0x1d7) [0x45cac7]
[ 4947.742] 7: /usr/bin/X (0x400000+0x35062) [0x435062]
[ 4947.742] 8: /usr/bin/X (0x400000+0x2184b) [0x42184b]
[ 4947.742] 9: /lib/libc.so.6 (__libc_start_main+0xfe) [0x7f39511cfd8e]
[ 4947.742] 10: /usr/bin/X (0x400000+0x213d9) [0x4213d9]
[ 4947.742] Segmentation fault at address 0x18
[ 4947.742]
Caught signal 11 (Segmentation fault). Server aborting
[ 4947.742]
Please consult the The X.Org Foundation support
  at http://wiki.x.org
 for help.
[ 4947.742] Please also check the log file at "/var/log/Xorg.1.log" for additional information.