The kernel log contains two instances of the same oops. I think this corresponds to when I unplugged the DisplayPort cable.
Apr 7 15:07:55 adar-dev kernel: [ 267.333834] BUG: unable to handle kernel NULL pointer dereference at 0000000000000230 Apr 7 15:07:55 adar-dev kernel: [ 267.336276] IP: [<ffffffffa0257be9>] intel_dp_link_down+0x1a9/0x2e0 [i915] Apr 7 15:07:55 adar-dev kernel: [ 267.339058] PGD 0 Apr 7 15:07:55 adar-dev kernel: [ 267.341778] Oops: 0000 [#1] SMP Apr 7 15:07:55 adar-dev kernel: [ 267.344481] last sysfs file: /sys/devices/virtual/backlight/acpi_video0/actual_brightness Apr 7 15:07:55 adar-dev kernel: [ 267.347210] CPU 0 Apr 7 15:07:55 adar-dev kernel: [ 267.347232] Modules linked in: snd_hda_codec_hdmi snd_hda_codec_conexant rfcomm binfmt_misc sco bnep l2cap ppdev parport_pc nfsd exportfs nfs lockd fscache nfs_acl auth_rpcgss sunrpc snd_hda_intel thinkpad_acpi snd_hda_codec arc4 snd_seq_midi snd_hwdep snd_rawmidi snd_pcm snd_seq_midi_event btusb usb_storage snd_seq iwlagn i915 uas uvcvideo videodev snd_timer snd_seq_device bluetooth iwlcore psmouse v4l2_compat_ioctl32 hid_ntrig joydev tpm_tis snd serio_raw drm_kms_helper mac80211 nvram drm tpm intel_ips soundcore tpm_bios snd_page_alloc cfg80211 i2c_algo_bit video lp parport usbhid hid ahci sdhci_pci sdhci libahci e1000e Apr 7 15:07:55 adar-dev kernel: [ 267.362003] Apr 7 15:07:55 adar-dev kernel: [ 267.364962] Pid: 250, comm: kworker/0:2 Not tainted 2.6.38-8-generic #41 LENOVO 2901CTO/2901CTO Apr 7 15:07:55 adar-dev kernel: [ 267.368021] RIP: 0010:[<ffffffffa0257be9>] [<ffffffffa0257be9>] intel_dp_link_down+0x1a9/0x2e0 [i915] Apr 7 15:07:55 adar-dev kernel: [ 267.371113] RSP: 0018:ffff88022f005890 EFLAGS: 00010286 Apr 7 15:07:55 adar-dev kernel: [ 267.374203] RAX: 00000000e01c004c RBX: ffff880230faf400 RCX: 0000000000000000 Apr 7 15:07:55 adar-dev kernel: [ 267.377315] RDX: 00000000801c0048 RSI: 00000000000e4100 RDI: ffff8802320c8000 Apr 7 15:07:55 adar-dev kernel: [ 267.380449] RBP: ffff88022f0058e0 R08: ffff88022f004000 R09: 0000000000000001 Apr 7 15:07:55 adar-dev kernel: [ 267.383731] R10: 0000000000000000 R11: 00000000ffffffff R12: ffff8802320c8000 Apr 7 15:07:55 adar-dev kernel: [ 267.386912] R13: ffff88022f6b8800 R14: 00000000801c0048 R15: 0000000000000000 Apr 7 15:07:55 adar-dev kernel: [ 267.390110] FS: 0000000000000000(0000) GS:ffff8800bb000000(0000) knlGS:0000000000000000 Apr 7 15:07:55 adar-dev kernel: [ 267.393344] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b Apr 7 15:07:55 adar-dev kernel: [ 267.396587] CR2: 0000000000000230 CR3: 0000000001a03000 CR4: 00000000000006f0 Apr 7 15:07:55 adar-dev kernel: [ 267.399799] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Apr 7 15:07:55 adar-dev kernel: [ 267.402992] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Apr 7 15:07:55 adar-dev kernel: [ 267.406172] Process kworker/0:2 (pid: 250, threadinfo ffff88022f004000, task ffff88022fb48000) Apr 7 15:07:55 adar-dev kernel: [ 267.409373] Stack: Apr 7 15:07:55 adar-dev kernel: [ 267.412568] ffff88022f6b8be8 ffff88022f6b8be8 ffff88022f005900 ffffffffc01c0048 Apr 7 15:07:55 adar-dev kernel: [ 267.415842] ffff88022f005900 ffff880230faf400 ffff88022f6b8800 0000000000000003 Apr 7 15:07:55 adar-dev kernel: [ 267.419119] 00000000f01c004c 00000000000e4100 ffff88022f005930 ffffffffa02582e6 Apr 7 15:07:55 adar-dev kernel: [ 267.422417] Call Trace: Apr 7 15:07:55 adar-dev kernel: [ 267.425684] [<ffffffffa02582e6>] intel_dp_dpms+0x66/0x160 [i915] Apr 7 15:07:55 adar-dev kernel: [ 267.428933] [<ffffffffa01afb9a>] drm_encoder_disable+0x2a/0x40 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.432205] [<ffffffffa01b07c8>] drm_crtc_helper_set_mode+0x3e8/0x4a0 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.435527] [<ffffffffa01b16a8>] drm_crtc_helper_set_config+0x838/0xa20 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.438776] [<ffffffff812da8c1>] ? idr_get_new_above+0x11/0x50 Apr 7 15:07:55 adar-dev kernel: [ 267.442032] [<ffffffffa01af5fc>] drm_fb_helper_set_par+0x7c/0xf0 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.445297] [<ffffffffa01af7c0>] drm_fb_helper_single_fb_probe+0x150/0x2d0 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.448547] [<ffffffffa01af544>] drm_fb_helper_hotplug_event+0x104/0x140 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.451792] [<ffffffffa025fdcc>] intel_fb_output_poll_changed+0x1c/0x20 [i915] Apr 7 15:07:55 adar-dev kernel: [ 267.455051] [<ffffffffa01b039c>] output_poll_execute+0x19c/0x1a0 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.458333] [<ffffffffa01b0200>] ? output_poll_execute+0x0/0x1a0 [drm_kms_helper] Apr 7 15:07:55 adar-dev kernel: [ 267.461611] [<ffffffff8107f7a3>] process_one_work+0x123/0x450 Apr 7 15:07:55 adar-dev kernel: [ 267.464850] [<ffffffff81082957>] worker_thread+0x177/0x420 Apr 7 15:07:55 adar-dev kernel: [ 267.468052] [<ffffffff810827e0>] ? worker_thread+0x0/0x420 Apr 7 15:07:55 adar-dev kernel: [ 267.471228] [<ffffffff81086bd6>] kthread+0x96/0xa0 Apr 7 15:07:55 adar-dev kernel: [ 267.474383] [<ffffffff8100cea4>] kernel_thread_helper+0x4/0x10 Apr 7 15:07:55 adar-dev kernel: [ 267.477481] [<ffffffff81086b40>] ? kthread+0x0/0xa0 Apr 7 15:07:55 adar-dev kernel: [ 267.480548] [<ffffffff8100cea0>] ? kernel_thread_helper+0x0/0x10 Apr 7 15:07:55 adar-dev kernel: [ 267.483647] Code: 75 00 8b 43 60 49 03 44 24 18 8b 00 e9 c8 fe ff ff 90 4c 8b 7b 30 8b 73 60 41 81 e6 ff ff ff bf 4c 89 e7 44 89 f2 e8 17 de ff ff <41> 8b b7 30 02 00 00 4c 89 ef e8 a8 47 fe ff eb 9e eb 04 90 90 Apr 7 15:07:55 adar-dev kernel: [ 267.490770] RIP [<ffffffffa0257be9>] intel_dp_link_down+0x1a9/0x2e0 [i915] Apr 7 15:07:55 adar-dev kernel: [ 267.494205] RSP <ffff88022f005890> Apr 7 15:07:55 adar-dev kernel: [ 267.497588] CR2: 0000000000000230 Apr 7 15:07:55 adar-dev kernel: [ 267.500924] ---[ end trace 741c9a2e54c739bf ]--- -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/754146 Title: DisplayPort-based external monitor cannot be enabled -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
