I'm trying to use some OpenGL element in multiple pipelines (differents GMainContext) in a process. In this case, I observed multiple segfault in XOpenDisplay, XCloseDisplay, gst_gl_shader_compile probably due to concurrent access (see the backtrace log). With my knowledge, Xlib isn't well know for this robustness in multiple threaded context, and it isn't possible to share the same display object between the pipelines (instanced by GstGLWindow_X11). 

As Matthew Waters said in the mailing, it should work.

Reproduction rate : 
Corruption with gst_gl_shader_compile, almost all the first time
Segmentation, 1/10 approx

Mailing reference : 
http://gstreamer-devel.966125.n4.nabble.com/OpenGL-Segfault-when-using-opengl-elements-in-multiple-pipelines-td4665772.html#a4665783

Environment : 
Arch linux with lastest version of gstreamer, mesa (10.1),  xf86-video-intel. 

Test application : 
http://pastebin.com/1RWud2Ns

Video sample used : 
http://www.auby.no/files/video_tests/h264_1080p_hp_4.1_10mbps_dts_unstyled_subs_monsters.mkv

Complete threads backtrace : 
http://pastebin.com/YbHNDJtj

Thread 1 : 

+ Trace 233277

Valgrind log : 
Vaapi : http://pastebin.com/cwFnACcc significant ? 

OpenGL : http://pastebin.com/bWPLHqzS

I will try to add more informations about this bug in the following week.