Cannot reach the ttys, and Xorg goes to Zombie process.

Jan 19 03:52:33 chef01 kernel: Modules linked in: binfmt_misc(E) cpufreq_ondemand(E) tun(E) egalax_ts_serial(E) i915(E) joydev(E) hid_generic(E) usbhid(E) snd_hda_codec_realtek(
Jan 19 03:52:33 chef01 kernel:  nf_conntrack_ipv4(E) nf_defrag_ipv4(E) nf_nat(E) xt_connmark(E) nf_conntrack(E) ip6_tables(E) iptable_mangle(E)
Jan 19 03:52:33 chef01 kernel: CPU: 1 PID: 313 Comm: Xorg.bin Tainted: G            E   4.4.0 #1
Jan 19 03:52:33 chef01 kernel: Hardware name: SI SL20/SL20, BIOS 080016  04/01/2013
Jan 19 03:52:33 chef01 kernel:  ffffffffa0174c3f ffff8800741bb990 ffffffff8075359d 0000000000000000
Jan 19 03:52:33 chef01 kernel:  ffff8800741bb9c8 ffffffff8048fa08 ffff88007ba6d0c0 ffff88007b4d43c0
Jan 19 03:52:33 chef01 kernel:  ffff88007b4d43c0 ffff880056e8d000 ffff88007b8e9000 ffff8800741bb9d8
Jan 19 03:52:33 chef01 kernel: Call Trace:
Jan 19 03:52:33 chef01 kernel:  [<ffffffff8075359d>] dump_stack+0x44/0x57
Jan 19 03:52:33 chef01 kernel:  [<ffffffff8048fa08>] warn_slowpath_common+0x88/0xc0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff8048fafa>] warn_slowpath_null+0x1a/0x20
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa01657b3>] kref_get.part.9+0x1e/0x27 [drm]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa0151601>] drm_framebuffer_reference+0x51/0x60 [drm]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa0161ead>] drm_atomic_set_fb_for_plane+0x2d/0x90 [drm]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa01d35e0>] __drm_atomic_helper_set_config+0xd0/0x3b0 [drm_kms_helper]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa01d4506>] restore_fbdev_mode+0x1f6/0x260 [drm_kms_helper]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa01d65e3>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa01d665c>] drm_fb_helper_set_par+0x2c/0x50 [drm_kms_helper]
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa032153a>] intel_fbdev_set_par+0x1a/0x60 [i915]
Jan 19 03:52:33 chef01 kernel:  [<ffffffff807c18b1>] fb_set_var+0x191/0x400
Jan 19 03:52:33 chef01 kernel:  [<ffffffff804be317>] ? update_curr+0x67/0x130
Jan 19 03:52:33 chef01 kernel:  [<ffffffff804bcd8c>] ? __enqueue_entity+0x6c/0x70
Jan 19 03:52:33 chef01 kernel:  [<ffffffff804c13ca>] ? enqueue_entity+0x34a/0x900
Jan 19 03:52:33 chef01 kernel:  [<ffffffff807b88fc>] fbcon_blank+0x1bc/0x2b0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff808410ba>] do_unblank_screen+0xba/0x1c0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff8083774a>] complete_change_console+0x5a/0xe0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff808386ed>] vt_ioctl+0xf1d/0x10d0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff80595b82>] ? do_wp_page+0x1d2/0x4d0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff80586003>] ? __inc_zone_page_state+0x33/0x40
Jan 19 03:52:33 chef01 kernel:  [<ffffffff805cb005>] ? mem_cgroup_end_page_stat+0x5/0x50
Jan 19 03:52:33 chef01 kernel:  [<ffffffffa014b8b0>] ? drm_setmaster_ioctl+0xf0/0xf0 [drm]
Jan 19 03:52:33 chef01 kernel:  [<ffffffff8082bf34>] tty_ioctl+0x3d4/0xbc0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff80597995>] ? handle_mm_fault+0xca5/0x16f0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff806e6867>] ? selinux_file_ioctl+0x107/0x1d0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff805ee61d>] do_vfs_ioctl+0x2cd/0x4b0
Jan 19 03:52:33 chef01 kernel:  [<ffffffff806dff43>] ? security_file_ioctl+0x43/0x60
Jan 19 03:52:33 chef01 kernel:  [<ffffffff805ee879>] SyS_ioctl+0x79/0x90
Jan 19 03:52:33 chef01 kernel:  [<ffffffff80ab24f6>] entry_SYSCALL_64_fastpath+0x16/0x75
Jan 19 03:52:33 chef01 kernel: ---[ end trace 80bfc40970d49658 ]---
Jan 19 03:52:33 chef01 kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000060
Jan 19 03:52:36 chef01 kernel: IP: [<ffffffffa031810c>] intel_fb_obj_invalidate+0x1c/0x100 [i915]
Jan 19 03:52:36 chef01 kernel: PGD 74107067 PUD 741a2067 PMD 0 
Jan 19 03:52:36 chef01 kernel: Oops: 0000 [#1] SMP