Not sure it is related to actual freezing incidents, but I saw this in kernel log at suspend:
Apr 2 09:46:26 lhs kernel: [ 305.963399] ------------[ cut here ]------------ Apr 2 09:46:26 lhs kernel: [ 305.963436] WARNING: CPU: 2 PID: 2892 at /build/buildd/linux-3.13.0/drivers/gpu/drm/i915/intel_uncore.c:125 gen6_gt_check_fifodbg.isra.9+0x38/0x50 [i915]() Apr 2 09:46:26 lhs kernel: [ 305.963437] MMIO read or write has been dropped ffffffff Apr 2 09:46:26 lhs kernel: [ 305.963488] Modules linked in: ctr ccm snd_hda_codec_hdmi snd_hda_codec_realtek joydev dell_wmi sparse_keymap pn544_mei mei_phy pn544 hci nfc ppdev intel_rapl x86_pkg_temp_thermal intel_powerclamp cor etemp dell_laptop dcdbas kvm_intel arc4 kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd psmouse serio_raw btusb wmi bnep rfcomm bluetooth iwlmvm mac80211 snd_h da_intel snd_hda_codec snd_hwdep uvcvideo snd_pcm iwlwifi videobuf2_vmalloc videobuf2_memops videobuf2_core snd_page_alloc i915 snd_seq_midi snd_seq_midi_event snd_rawmidi parport_pc videodev video cfg80211 snd_seq snd_seq_device dr m_kms_helper snd_timer drm lpc_ich snd mac_hid mei_me i2c_algo_bit mei soundcore lp nls_iso8859_1 parport e1000e ahci libahci ptp pps_core Apr 2 09:46:26 lhs kernel: [ 305.963491] CPU: 2 PID: 2892 Comm: kworker/u8:12 Not tainted 3.13.0-21-generic #43-Ubuntu Apr 2 09:46:26 lhs kernel: [ 305.963492] Hardware name: Dell Inc. Latitude E7440/07F3F4, BIOS A08 02/18/2014 Apr 2 09:46:26 lhs kernel: [ 305.963515] Workqueue: i915 gen6_force_wake_work [i915] Apr 2 09:46:26 lhs kernel: [ 305.963520] 0000000000000009 ffff8803c2935d38 ffffffff81714914 ffff8803c2935d80 Apr 2 09:46:26 lhs kernel: [ 305.963523] ffff8803c2935d70 ffffffff810676bd ffff880406c48020 ffff880406c48028 Apr 2 09:46:26 lhs kernel: [ 305.963526] 0000000000000246 0000000000000000 0000000000000100 ffff8803c2935dd0 Apr 2 09:46:26 lhs kernel: [ 305.963527] Call Trace: Apr 2 09:46:26 lhs kernel: [ 305.963534] [<ffffffff81714914>] dump_stack+0x45/0x56 Apr 2 09:46:26 lhs kernel: [ 305.963538] [<ffffffff810676bd>] warn_slowpath_common+0x7d/0xa0 Apr 2 09:46:26 lhs kernel: [ 305.963540] [<ffffffff8106772c>] warn_slowpath_fmt+0x4c/0x50 Apr 2 09:46:26 lhs kernel: [ 305.963547] [<ffffffff8109a65a>] ? try_to_wake_up+0x1fa/0x2c0 Apr 2 09:46:26 lhs kernel: [ 305.963568] [<ffffffffa02b6de8>] gen6_gt_check_fifodbg.isra.9+0x38/0x50 [i915] Apr 2 09:46:26 lhs kernel: [ 305.963585] [<ffffffffa02b6e8b>] __gen6_gt_force_wake_mt_put+0x2b/0x30 [i915] Apr 2 09:46:26 lhs kernel: [ 305.963602] [<ffffffffa02b6bb7>] gen6_force_wake_work+0x37/0x50 [i915] Apr 2 09:46:26 lhs kernel: [ 305.963606] [<ffffffff81083892>] process_one_work+0x182/0x450 Apr 2 09:46:26 lhs kernel: [ 305.963610] [<ffffffff81084631>] worker_thread+0x121/0x410 Apr 2 09:46:26 lhs kernel: [ 305.963614] [<ffffffff81084510>] ? rescuer_thread+0x3e0/0x3e0 Apr 2 09:46:26 lhs kernel: [ 305.963617] [<ffffffff8108b302>] kthread+0xd2/0xf0 Apr 2 09:46:26 lhs kernel: [ 305.963620] [<ffffffff8108b230>] ? kthread_create_on_node+0x1d0/0x1d0 Apr 2 09:46:26 lhs kernel: [ 305.963624] [<ffffffff8172523c>] ret_from_fork+0x7c/0xb0 Apr 2 09:46:26 lhs kernel: [ 305.963627] [<ffffffff8108b230>] ? kthread_create_on_node+0x1d0/0x1d0 Apr 2 09:46:26 lhs kernel: [ 305.963629] ---[ end trace 396fb56d04ab9b14 ]--- Apr 2 09:46:26 lhs kernel: [ 306.542815] PM: suspend of devices complete after 599.849 msecs Apr 2 09:46:26 lhs kernel: [ 306.543013] PM: late suspend of devices complete after 0.196 msecs
Not sure it is related to actual freezing incidents, but I saw this in kernel log at suspend:
Apr 2 09:46:26 lhs kernel: [ 305.963399] ------------[ cut here ]------------ buildd/ linux-3. 13.0/drivers/ gpu/drm/ i915/intel_ uncore. c:125 gen6_gt_ check_fifodbg. isra.9+ 0x38/0x50 [i915]() codec_realtek joydev dell_wmi sparse_keymap pn544_mei mei_phy pn544 hci nfc ppdev intel_rapl x86_pkg_ temp_thermal intel_powerclamp cor wake_work [i915] 914>] dump_stack+ 0x45/0x56 6bd>] warn_slowpath_ common+ 0x7d/0xa0 72c>] warn_slowpath_ fmt+0x4c/ 0x50 65a>] ? try_to_ wake_up+ 0x1fa/0x2c0 de8>] gen6_gt_ check_fifodbg. isra.9+ 0x38/0x50 [i915] e8b>] __gen6_ gt_force_ wake_mt_ put+0x2b/ 0x30 [i915] bb7>] gen6_force_ wake_work+ 0x37/0x50 [i915] 892>] process_ one_work+ 0x182/0x450 631>] worker_ thread+ 0x121/0x410 510>] ? rescuer_ thread+ 0x3e0/0x3e0 302>] kthread+0xd2/0xf0 230>] ? kthread_ create_ on_node+ 0x1d0/0x1d0 23c>] ret_from_ fork+0x7c/ 0xb0 230>] ? kthread_ create_ on_node+ 0x1d0/0x1d0
Apr 2 09:46:26 lhs kernel: [ 305.963436] WARNING: CPU: 2 PID: 2892 at /build/
Apr 2 09:46:26 lhs kernel: [ 305.963437] MMIO read or write has been dropped ffffffff
Apr 2 09:46:26 lhs kernel: [ 305.963488] Modules linked in: ctr ccm snd_hda_codec_hdmi snd_hda_
etemp dell_laptop dcdbas kvm_intel arc4 kvm crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd psmouse serio_raw btusb wmi bnep rfcomm bluetooth iwlmvm mac80211 snd_h
da_intel snd_hda_codec snd_hwdep uvcvideo snd_pcm iwlwifi videobuf2_vmalloc videobuf2_memops videobuf2_core snd_page_alloc i915 snd_seq_midi snd_seq_midi_event snd_rawmidi parport_pc videodev video cfg80211 snd_seq snd_seq_device dr
m_kms_helper snd_timer drm lpc_ich snd mac_hid mei_me i2c_algo_bit mei soundcore lp nls_iso8859_1 parport e1000e ahci libahci ptp pps_core
Apr 2 09:46:26 lhs kernel: [ 305.963491] CPU: 2 PID: 2892 Comm: kworker/u8:12 Not tainted 3.13.0-21-generic #43-Ubuntu
Apr 2 09:46:26 lhs kernel: [ 305.963492] Hardware name: Dell Inc. Latitude E7440/07F3F4, BIOS A08 02/18/2014
Apr 2 09:46:26 lhs kernel: [ 305.963515] Workqueue: i915 gen6_force_
Apr 2 09:46:26 lhs kernel: [ 305.963520] 0000000000000009 ffff8803c2935d38 ffffffff81714914 ffff8803c2935d80
Apr 2 09:46:26 lhs kernel: [ 305.963523] ffff8803c2935d70 ffffffff810676bd ffff880406c48020 ffff880406c48028
Apr 2 09:46:26 lhs kernel: [ 305.963526] 0000000000000246 0000000000000000 0000000000000100 ffff8803c2935dd0
Apr 2 09:46:26 lhs kernel: [ 305.963527] Call Trace:
Apr 2 09:46:26 lhs kernel: [ 305.963534] [<ffffffff81714
Apr 2 09:46:26 lhs kernel: [ 305.963538] [<ffffffff81067
Apr 2 09:46:26 lhs kernel: [ 305.963540] [<ffffffff81067
Apr 2 09:46:26 lhs kernel: [ 305.963547] [<ffffffff8109a
Apr 2 09:46:26 lhs kernel: [ 305.963568] [<ffffffffa02b6
Apr 2 09:46:26 lhs kernel: [ 305.963585] [<ffffffffa02b6
Apr 2 09:46:26 lhs kernel: [ 305.963602] [<ffffffffa02b6
Apr 2 09:46:26 lhs kernel: [ 305.963606] [<ffffffff81083
Apr 2 09:46:26 lhs kernel: [ 305.963610] [<ffffffff81084
Apr 2 09:46:26 lhs kernel: [ 305.963614] [<ffffffff81084
Apr 2 09:46:26 lhs kernel: [ 305.963617] [<ffffffff8108b
Apr 2 09:46:26 lhs kernel: [ 305.963620] [<ffffffff8108b
Apr 2 09:46:26 lhs kernel: [ 305.963624] [<ffffffff81725
Apr 2 09:46:26 lhs kernel: [ 305.963627] [<ffffffff8108b
Apr 2 09:46:26 lhs kernel: [ 305.963629] ---[ end trace 396fb56d04ab9b14 ]---
Apr 2 09:46:26 lhs kernel: [ 306.542815] PM: suspend of devices complete after 599.849 msecs
Apr 2 09:46:26 lhs kernel: [ 306.543013] PM: late suspend of devices complete after 0.196 msecs