Dell xps started choking after latest upgrade (incl. kernel)

[netikras]

netikras@netikras-xps ~ $ inxi -F
System: Host: netikras-xps Kernel: 4.4.0-91-generic x86_64 (64 bit)
           Desktop: Cinnamon 3.0.7 Distro: Linux Mint 18 Sarah
Machine: System: Dell (portable) product: XPS 13 9350
           Mobo: Dell model: 0VM5NC v: A01
           Bios: Dell v: 1.2.3 date: 01/08/2016
CPU: Dual core Intel Core i7-6500U (-HT-MCP-) cache: 4096 KB
           clock speeds: max: 3100 MHz 1: 556 MHz 2: 623 MHz 3: 533 MHz
           4: 859 MHz
Graphics: Card: Intel Sky Lake Integrated Graphics
           Display Server: X.Org 1.18.4 drivers: intel (unloaded: fbdev,vesa)
           Resolution: 2560x1440@60.00hz
           GLX Renderer: Mesa DRI Intel HD Graphics 520 (Skylake GT2)
           GLX Version: 3.0 Mesa 17.0.7
Audio: Card Intel Sunrise Point-LP HD Audio driver: snd_hda_intel
           Sound: Advanced Linux Sound Architecture v: k4.4.0-91-generic
Network: Card: Broadcom BCM4350 802.11ac Wireless Network Adapter
           driver: brcmfmac
           IF: wlp58s0 state: up mac: [removed]
Drives: HDD Total Size: NA (-) ID-1: /dev/nvme0n1 model: N/A size: 512.1GB
Partition: ID-1: / size: 21G used: 16G (84%) fs: ext4 dev: /dev/nvme0n1p7
           ID-2: /home size: 190G used: 150G (84%) fs: ext4 dev: /dev/nvme0n1p8
           ID-3: swap-1 size: 10.24GB used: 0.00GB (0%) fs: swap dev: /dev/nvme0n1p6
RAID: No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors: System Temperatures: cpu: 50.0C mobo: N/A
           Fan Speeds (in rpm): cpu: N/A
Info: Processes: 285 Uptime: 6:19 Memory: 5455.3/15909.7MB
           Client: Shell (bash) inxi: 2.2.35
netikras@netikras-xps ~ $

Latest updates installed and laptop rebooted y-day.

So here's what happened. This morning I plugged the charger in and left laptop running. A few hours later its screen was already turned off (that's normal). However when I moved the mouse laptop display turned on and I could see the lock-screen. No matter what I did the lock screen was still there. Usually it goes away after I move the mouse for another second or so, but this time... nada. However the cursor was still responsive -- I could where it's moving.

I switched to TTY1 , logged in. Issued 's2ram' command ('suspend' -- a part of uswsusp package). To my surprise it.. froze. The s2ram command was telling me it is suspending the laptop, but nothing was happening.

I have seen cases like that -- usually it's caused by processes in D state. So I ran a 'ps aux | grep D' to see what's there.

What happened next scared me a little. ps command given above did show me a few results, and so far only one process was seen in D: [khugepaged]. I assumed this is somewhat swap-related and it's normal to see those processes in D sometimes. What scared me the most was that the ps command... never finished. I mean it was still hogging my shell after like 20 seconds.

I couldn't get the shell back on TTY1. So I switched to TTY2 and tried to shutdown the machine gracefully: shutdown -f -h now. No luck here... It just popped open the plymouth screen with LM logo and that's about it. after hitting [esc] there was only only log entry at the very top -- claiming, that plymouth screen is opening... Waited for a minute or so -- nothing happened. And I had to shut the laptop down forcefuly (damn it's a painful thing to do :/) .

After that OS rebooted fine (at least I think so). Nothing too fishy so far, but I don't like entries in kern.log. Would anybody please have a look?
I'm terrified by an idea it could be a hardware failure...

the '@' parts are binary zeroes. I'm worried by two things: the DRM errors and stacktraces below. I'm praying to Linus that these are only related to upgrading kernel and not to CPU or memory fault... :(