Comment 29 for bug 1174495

I can also confirm this bug on Fedora 18 X86_64, radeon driver, HD5870 card.
I cannot log into the system with two external monitors attached, but with only one external monitor it works fine. This seems to have started to happen after upgrade to mesa-dri-drivers 9.1-1 or 9.1-3 (I did not restart between those updates). Here is my backtrace:
b7b62d4d01e98c8b31d95895cbede393b8b0c6e8 0x8954b __memset_sse2 /lib64/libc.so.6 45eccba94f5fef95c8933974ac014d83e50a9ebb
c9e82f1ca30be88ed6ef697aa581a1c940858291 0x349ff2 r600_texture_create_object /usr/lib64/dri/r600_dri.so 4f51004f888b1ba8194719f476c2fd4ff4aad900
c9e82f1ca30be88ed6ef697aa581a1c940858291 0x34a2c7 r600_texture_create /usr/lib64/dri/r600_dri.so 5baaed899c5ecf15a1568310eff18dc385cdf50d
c9e82f1ca30be88ed6ef697aa581a1c940858291 0x35ca25 dri2_allocate_textures /usr/lib64/dri/r600_dri.so 0a2fa38b05320f36fa5b90de563948aac101910e
c9e82f1ca30be88ed6ef697aa581a1c940858291 0x35b595 dri_st_framebuffer_validate /usr/lib64/dri/r600_dri.so 45eccba94f5fef95c8933974ac014d83e50a9ebb
c9e82f1ca30be88ed6ef697aa581a1c940858291 0x35b7ce dri_set_tex_buffer2 /usr/lib64/dri/r600_dri.so 55f8abe768545f45025c61cca676f0352439722d
67f4899c1db4d10dd1558ccbb7b8fad4e81e3379 0x68702 _cogl_winsys_texture_pixmap_x11_update /lib64/libcogl.so.11 ac79bd8478de58b10ea1b2bbc9d920bfbe437214
67f4899c1db4d10dd1558ccbb7b8fad4e81e3379 0x66104 _cogl_texture_pixmap_x11_update /lib64/libcogl.so.11 96f709cfd3fe851395649feeda7d4dd459e3ca60
67f4899c1db4d10dd1558ccbb7b8fad4e81e3379 0x666ad _cogl_texture_pixmap_x11_get_texture /lib64/libcogl.so.11 6179db327fe5f11fb226532cabb471745b820c8f
67f4899c1db4d10dd1558ccbb7b8fad4e81e3379 0x66709 _cogl_texture_pixmap_x11_get_type /lib64/libcogl.so.11 ad318b56f9bf3c97e02782cfada93e8f37221c59
67f4899c1db4d10dd1558ccbb7b8fad4e81e3379 0x437d9 cogl_pipeline_set_layer_texture /lib64/libcogl.so.11 ba1ae932f4a148b027fd73337e04d05fbae9862e
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x33eb2 set_texture_on_actor /lib64/libmutter.so.0 47169c9a5b07212ae0061e199a81ca87080a2e4c
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x34008 set_texture /lib64/libmutter.so.0 6647294c524f089a0c77389826b0a954c997c085
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x3491f meta_background_actor_update /lib64/libmutter.so.0 184cb323b2f3eaf40fc3b375371bdf1393e6882a
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x3352a meta_compositor_process_event /lib64/libmutter.so.0 5c8e84a4b7a1c62daf4be566f862cf325d9b1926
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x45367 event_callback /lib64/libmutter.so.0 11cf28c10df323150560c808d8bf75e7ed72e0c8
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x8f476 filter_func /lib64/libmutter.so.0 7bfd96ce0e83046b4b4da64b6d99cf1d3ce823d6
1c54a46d2f8de1beadccfa39550b5eef67ab6bc0 0x4a901 gdk_event_apply_filters /lib64/libgdk-3.so.0 a28856cf0bdff41c2ad87be20d4186aeea868a26
1c54a46d2f8de1beadccfa39550b5eef67ab6bc0 0x4aad7 _gdk_x11_display_queue_events /lib64/libgdk-3.so.0 50da1079f5dfea096a6ddfd4caca8af2b76726e4
1c54a46d2f8de1beadccfa39550b5eef67ab6bc0 0x20511 gdk_display_get_event /lib64/libgdk-3.so.0 457cc16f8850789e7b3830330439fcf89b9a418b
1c54a46d2f8de1beadccfa39550b5eef67ab6bc0 0x4a812 gdk_event_source_dispatch /lib64/libgdk-3.so.0 d2af43c4e5d993f84766ffa06ddb024ac500e725
9442c0d3ccde3c8dbc81f858e03246a133f086d6 0x47a55 g_main_context_dispatch /lib64/libglib-2.0.so.0 d4b6d4f2836ef32bd9d5847446bdcc7c19cfa379
9442c0d3ccde3c8dbc81f858e03246a133f086d6 0x47d88 g_main_context_iterate.isra.24 /lib64/libglib-2.0.so.0 ba0d551b7f0614ded38071cba2b37e156703e7f2
9442c0d3ccde3c8dbc81f858e03246a133f086d6 0x48182 g_main_loop_run /lib64/libglib-2.0.so.0 97ad0c44e2f6c8d6c6037025add5aa29f54a351c
c043a38bda0d5dc29bb15a1e211273a4ec3dea5d 0x53467 meta_run /lib64/libmutter.so.0 0e5cc7fe0eb8f1fbe596e745f6fb64c36c5455ed
b7584e5ed0db7d29ef55ff77ab8344f06b0c3f94 0x1e2c main /usr/bin/gnome-shell bd96fec6192e77e3dbc72e49eae3be6a52f6ef62