There is an issue around currently for Red Hat based systems, Oracle Linux here, in version 7.3. running systemd version 219-30.0.1, having a shutdown or reboot seemingly hang on a failed swap unit (deallocation). A lot of posts on the net discuss the issue, After switching to Ubuntu 15.04 laptop won’t shutdown suggested the w/a, doing a swapoff/swapon bounce in advance, that worked for me, referencing reboot hangs at ‘Reached target Shutdown’. Systemd: Hangs indefinitely on >90% of reboot attempts comprises in in-depth analysis.
I’m not shure, though, whether tmp.mount.hm4: After swap.target is releated, really, because the implemented change is already present on my systems (systemd‘s). I’m much more tending to suspect widespread storage fragmentation on the swap area to cause the relatively long term swap off run-times. In addition, I almost only experienced the issue for systems that have been up for a longer number of days, say from 90 days onwards.
Bad is an unpleasant word, right? “On” or “off” implies some final statement, or “failed” may signal something wrong but at least terminated. But “bad”… uuuhh, blameworthy, guilty, unaccountable, still being around. Ok, before diving into linguistic depression, the change eventually turned out simple and was actually in good faith but, however, produced remarkable irritation. You know, 
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