Created attachment 115943 [details]
Xorg.0.log

System Environment:
--------------------------
Libdrm:		(master)libdrm-2.4.61
 Mesa:		(10.6)7c5cca5ee2c4076db45f89658e3a38098d6f828d
 Xserver:		(server-1.17-branch)xorg-server-1.17.1
 Xf86_video_intel:		(master)2.99.917
 Libva:		(master)9bfde38f19d81b7f33db8c4c8e80420c9e60429e
 Libva_intel_driver:		(master)3c66aa58ccb0fcb393472eeaa6a9188216683a79
 Kernel:   (drm-intel-fixes)54da691deb123c045259ebf4f5c67381244f58f1

Bug detailed description:
-----------------------------
Fail to start X on libdrm-2.4.61, it works well on libdrm-2.4.60

good commit: 5f7b6723e1bed755c230817eea0563bab5b2a8a7 
bad commit: b2360626c4aa1dccdf3fe258b833121748d64d35

output:
X.Org X Server 1.17.1
Release Date: 2015-02-10
X Protocol Version 11, Revision 0
Build Operating System: Linux 3.19.0 x86_64
Current Operating System: Linux x-hsw27 4.1.0-rc3_drm-intel-fixes_364aec_20150512+ #72 SMP Tue May 12 09:08:30 EDT 2015 x86_64
Kernel command line: BOOT_IMAGE=kernels//nightly_parents/2015_05_19/drm-intel-fixes/364aece01a2dd748fc36a1e8bf52ef639b0857bd/bzImage_x86_64 root=/dev/sda2 hostname=x-hsw27 modules_path=kernels//nightly_parents/2015_05_19/drm-intel-fixes/364aece01a2dd748fc36a1e8bf52ef639b0857bd/modules_x86_64/lib/modules/4.1.0-rc3_drm-intel-fixes_364aec_20150512+
Build Date: 20 May 2015  05:11:47PM

Current version of pixman: 0.33.1
        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: "/opt/X11R7/var/log/Xorg.0.log", Time: Thu May 21 16:12:27 2015
(==) Using config file: "/etc/X11/xorg.conf"
(==) Using system config directory "/opt/X11R7/share/X11/xorg.conf.d"
(EE)
(EE) Backtrace:
(EE) 0: X (OsSigHandler+0x29) [0x471389]
(EE) 1: /lib64/libpthread.so.0 (__restore_rt+0x0) [0x359040ef9f]
(EE) 2: ? (?+0x0) [0x0]
(EE)
(EE) Segmentation fault at address 0x0
(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 "/opt/X11R7/var/log/Xorg.0.log" for additional information.
(EE)
(EE) Server terminated with error (1). Closing log file.

Reproduce steps:
---------------------------- 
1. xinit