It might be related to the kernel’s watchdog code due to research by Linus Torvalds. “So I’m looking at the watchdog code, and it seems racy [with regard to] parking and startup…Quite frankly, I’m just grasping for straws here, but a lot of the watchdog traces really have seemed spurious…”

via [Phoronix] Nasty Lockup Issue Still Being Investigated For Linux 3.18.