Description of problem:
This happened when my laptop resumed from suspend. system was completely unresponsive (display showed old contents but no visible mouse pointer, did not react to keyboard).

This happens quite often (about every third time I try to resume) since upgrading from F20->F21.

lspci  | grep -i gm965:
00:00.0 Host bridge: Intel Corporation Mobile PM965/GM965/GL960 Memory Controller Hub (rev 0c)
00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (primary) (rev 0c)
00:02.1 Display controller: Intel Corporation Mobile GM965/GL960 Integrated Graphics Controller (secondary) (rev 0c)

Additional info:
reporter:       libreport-2.3.0
BUG: unable to handle kernel NULL pointer dereference at 0000000000000035
IP: [<ffffffffa0117811>] i915_error_state_to_str+0x781/0xa20 [i915]
PGD ba72c067 PUD b3ad0067 PMD 0 
Oops: 0002 [#1] SMP 
Modules linked in: fuse xt_CHECKSUM ipt_MASQUERADE tun ccm ip6t_rpfilter ip6t_REJECT xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw ipheth uvcvideo arc4 videobuf2_vmalloc videobuf2_memops coretemp iTCO_wdt iTCO_vendor_support gpio_ich videobuf2_core kvm_intel v4l2_common iwl4965 dell_wmi sparse_keymap kvm videodev iwlegacy dell_laptop media dcdbas mac80211 i2c_i801 serio_raw snd_hda_codec_idt snd_hda_codec_generic snd_hda_intel snd_hda_controller cfg80211 snd_hda_codec snd_hwdep snd_seq r592 memstick rfkill
 sdhci_pci snd_seq_device sdhci lpc_ich snd_pcm mfd_core snd_timer snd wmi soundcore shpchp acpi_cpufreq nfsd auth_rpcgss nfs_acl lockd binfmt_misc sunrpc dm_crypt i915 b44 mii i2c_algo_bit ssb firewire_ohci drm_kms_helper mmc_core firewire_core ata_generic drm pata_acpi crc_itu_t video
CPU: 1 PID: 3196 Comm: gnome-shell Not tainted 3.17.8-300.fc21.x86_64 #1
Hardware name: Dell Inc. Vostro 1500                     /0NX907, BIOS A06 04/21/2008
task: ffff8800d83de220 ti: ffff8800d96a0000 task.ti: ffff8800d96a0000
RIP: 0010:[<ffffffffa0117811>]  [<ffffffffa0117811>] i915_error_state_to_str+0x781/0xa20 [i915]
RSP: 0018:ffff8800d96a3d18  EFLAGS: 00010246
RAX: 00000000000000b0 RBX: ffff8800da1fa600 RCX: 0000000000000001
RDX: ffff8801193a0000 RSI: ffff8800da1fa600 RDI: 00000000000000b0
RBP: ffff8800d96a3dc8 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffffa0196360 R11: ffff8800d96a3e18 R12: 0000000000000000
R13: ffff88003617b000 R14: ffff8800d96a3e18 R15: ffff880114ae6a80
FS:  00007f9534854a40(0000) GS:ffff88011fd00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000035 CR3: 00000000b6380000 CR4: 00000000000007e0
Stack:
 ffff8800d96a3d50 ffffffffa00182bf ffff880114ae6a80 ffff8800da1fa600
 ffff8800d96a3d8c ffff88003617b000 ffff8800da1fa600 00000000d96a3d78
 ffffffffa00183d5 ffff8800da1fa600 00007fff64069190 00000000000000b0
Call Trace:
 [<ffffffffa00182bf>] ? drm_gem_handle_create_tail+0x9f/0x180 [drm]
 [<ffffffffa00183d5>] ? drm_gem_handle_create+0x35/0x40 [drm]
 [<ffffffffa010e6a4>] ? i915_gem_create+0x64/0x110 [i915]
 [<ffffffffa0018e6f>] drm_ioctl+0x1df/0x680 [drm]
 [<ffffffff810cda4b>] ? put_prev_entity+0x5b/0x400
 [<ffffffff810c865f>] ? set_next_entity+0x5f/0x80
 [<ffffffff810d0f69>] ? pick_next_task_fair+0x6c9/0x8c0
 [<ffffffff812211c0>] do_vfs_ioctl+0x2d0/0x4b0
 [<ffffffff81221421>] SyS_ioctl+0x81/0xa0
 [<ffffffff81135f66>] ? __audit_syscall_exit+0x1f6/0x2a0
 [<ffffffff81748ca9>] system_call_fastpath+0x16/0x1b
Code: 46 8b 44 20 04 42 8b 0c 20 42 8b 44 20 0c 49 83 c4 10 89 04 24 31 c0 e8 6e f5 ff ff 49 81 fc 00 04 00 00 75 c5 49 8b b6 f8 01 00 <00> 48 85 f6 74 08 48 89 df e8 41 a2 03 00 49 8b 96 00 02 00 00 
RIP  [<ffffffffa0117811>] i915_error_state_to_str+0x781/0xa20 [i915]
 RSP <ffff8800d96a3d18>
CR2: 0000000000000035