Created attachment 15994 [details]
test case

When call glReadPixel, it seg fault with bt info:


#0  0xb7aba36e in i915_emit_state (intel=0x8058728) at i915_vtbl.c:325
#1  0xb7ac787c in intelRenderStart (ctx=0x8058728) at intel_tris.c:917
#2  0xb7aa2de1 in intel_run_render (ctx=0x8058728, stage=0x809b834)
    at intel_render.c:217
#3  0xb7b66ebf in _tnl_run_pipeline (ctx=0x8058728) at tnl/t_pipeline.c:158
#4  0xb7ac78e9 in intelRunPipeline (ctx=0x8058728) at intel_tris.c:906
#5  0xb7b67428 in _tnl_draw_prims (ctx=0x8058728, arrays=0x8089d40, 
    prim=0x808889c, nr_prims=1, ib=0x0, min_index=0, max_index=3)
    at tnl/t_draw.c:402
#6  0xb7b5f9e1 in vbo_exec_vtx_flush (exec=0x8088778)
    at vbo/vbo_exec_draw.c:215
#7  0xb7b5b208 in vbo_exec_FlushVertices (ctx=0x8058728, flags=1)
    at vbo/vbo_exec_api.c:700
#8  0xb7bff8e1 in _mesa_ReadPixels (x=50, y=50, width=1, height=1, 
    format=6407, type=5126, pixels=0xbffdb148) at main/drawpix.c:294
#9  0x0804894c in test () at mustpass2.c:31
#10 0x080489c3 in display () at mustpass2.c:44
#11 0xb7f0d757 in processWindowWorkList (window=0x804f448) at glut_event.c:1306
#12 0xb7f0e3b8 in glutMainLoop () at glut_event.c:1353
#13 0x08048a3f in main (argc=1, argv=0xbffe5034) at testcase.c:56