This bug seems to be the closest match to what I'm experiencing. I'm hitting similar trouble on desktop/graphical Ubuntu on some Dell laptops.
Ubuntu 16.04 AMD64. Happening on kernel versions 4.13.0-38 and 4.4.0-116. I've tried version 4.4.0-117 as posted by @kamalmostafa - same result. The laptops are an XPS 13 and a Precision M3520. Both machines have Kaby Lake/7th gen Core i7 CPUs. The problem on the 4.4.0-116 kernel (on my M3520) occurred the first reboot after updating the Intel microcode. I'm starting to think this is related to the Meltdown/Spectre patching. I started sssd in the foreground with debug set to 9 on the M3520 and netcat'd the results to another machine, so I think I have it right up until the laptop stops responding. It's obviously quite verbose, but if someone thinks it'll help, I'll post it. >From talking to some of the people on #ubuntu-server, the microcode does seem to be increasingly likely the root cause. Bug #1759920 may include relevant information. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1746806 Title: sssd appears to crash AWS c5 and m5 instances, cause 100% CPU Status in cloud-images: Fix Released Status in linux package in Ubuntu: In Progress Status in linux-aws package in Ubuntu: Confirmed Status in linux source package in Xenial: In Progress Status in linux-aws source package in Xenial: In Progress Bug description: After upgrading to the Ubuntu EC2 AMI from 20180126 (specifically ami-79873901 in us-west-2) we have seen sssd hard locking c5 and m5 EC2 instances after starting the service and CPU goes to 100%. We do not experience this issue with t2 or c4 instance types and we do not see this issue on any instance types using Ubuntu Cloud images from 20180109 or before. I have verified that this is kernel related as I booted an image that we created using the Ubuntu cloud image from 20180109 which works fine on a c5. I then did a "apt update && apt install --only-upgrade linux-aws && systemctl disable sssd", rebooted the server, verified I was on the new kernel and started sssd with "systemctl start sssd" and the EC2 instance froze and Cloudwatch CPU usage for that instance went to 100%. I haven't been able to find much in the syslog, kern.log, journalctl logs, etc. The only thing I have been able to find is that when this happens I tend to see "^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@" in the syslog and sssd log files. I have attached several log files and the output of a "apport-bug /usr/sbin/sssd". Let me know if you need anything else to help track this down. Thanks, Paul To manage notifications about this bug go to: https://bugs.launchpad.net/cloud-images/+bug/1746806/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : firstname.lastname@example.org Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp