Comment 6 for bug 1019708

This bad behavior seems to have been caused by issues with futex system calls. Here's the most detailed description I've seen so far, including a small test program that can be used to replicate the behavior (I haven't tried it since it modifies the system time):

https://lwn.net/Articles/504658/

Rather than rebooting, simply setting the system time manually or finding some other way to call settimeofday() would have also restored normal behavior.