[i965] X freeze while running repro script

gdb backtrace:

(gdb) bt full
#0 0x00007f4b28252cd7 in ioctl () from /lib/libc.so.6
No symbol table info available.
#1 0x00007f4b261c15af in ?? () from /usr/lib/libdrm_intel.so.1
No symbol table info available.
#2 0x00007f4b155ac75f in _intel_batchbuffer_flush () from /usr/lib/dri/i965_dri.so
No symbol table info available.
#3 0x00007f4b26ecbc4c in __glXDRIenterServer (rendering=<value optimized out>) at ../../glx/glxdri.c:172
 i = 0
#4 0x00007f4b26ec2dec in __glXDispatch (client=0x51037b0) at ../../glx/glxext.c:525
 stuff = (xGLXSingleReq *) 0x95a42f0
 opcode = <value optimized out>
 cl = (__GLXclientState *) 0x50cf670
 retval = 0
#5 0x000000000044e304 in Dispatch () at ../../dix/dispatch.c:437
 result = <value optimized out>
 client = (ClientPtr) 0x51037b0
 nready = 0
 start_tick = 119740
#6 0x0000000000433d8d in main (argc=10, argv=0x7fff32677248, envp=<value optimized out>) at ../../dix/main.c:397
 i = 1
 alwaysCheckForInput = {0, 1}
(gdb) quit

I should also point out that I am unlikely to run that particular kernel for any other purposes than debugging this issue, as the iwl3945 included in it refuses to associate with my access point (firmware appears to get loaded properly).

Oh, one last thing: I default to using a vesa framebuffer console (vga=0x31b on the kernel command line), and with that kernel the vesa console doesn't display anything at all, only X works.

probably another dupe of 359392