Arch Linux

Problem: Machine does not reliability poweroff on a shutdown under 4.4.1.
Work-around: Downgrading to a 4.3.x kernel fixes the hung shutdown.

Since updating to the 4.4.1 kernel, my Haswell machine fails to poweroff about 40% of the time. I don't see anything in `journalctl -b -1` that indicates an error or warning, so I'm thinking whatever is happening occurs after the journal logging as evident by the last few lines lines (complete journalctl is attached):
...
Feb 14 11:02:41 quartz systemd[1]: Reached target Shutdown.
Feb 14 11:02:41 quartz systemd[1]: Reached target Final Step.
Feb 14 11:02:41 quartz systemd[1]: Starting Power-Off...
Feb 14 11:02:41 quartz systemd[1]: Shutting down.
Feb 14 11:02:41 quartz systemd-shutdown[1]: Sending SIGTERM to remaining processes...
Feb 14 11:02:41 quartz systemd-journald[186]: Journal stopped

However, on the screen, I the following displayed which repeat every 2 min until I hold in the power button:
INFO: task shutdown:1 block for more then 120 seconds.
Not tainted 4.4.1-2-ARCH #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
INFO: task kworker/0:3:1642 block for more than 120 seconds.
Not tainted 4.4.1-2-ARCH #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
...

Note that  FS#45863  has the same error (task shutdown:1 block for more then 120 seconds.) and similar symptoms, but mine is cleaner lacking all of the other output in that FS.

Additional info:
* package version(s) 4.4.1-2-ARCH
* config and/or log files etc.


Steps to reproduce:
1) Issue `shutdown -h now` ... 4 times out of 10 the above happens.

CPU: i3-4130T
MB: MSI MS-7851/H97I AC (MS-7851)