Hey, I've had that bug! The whole computer freezes for up to a minute and then you get a dmesg stack trace:

    Kernel panic - not syncing: Watchdog detected hard LOCKUP on cpu 3
    CPU: 3 PID: 17176 Comm: trinity-c95 Not tainted 3.17.0+ #87
    0000000000000000 00000000f3a61725 ffff880244606bf0 ffffffff9583e9fa
    ffffffff95c67918 ffff880244606c78 ffffffff9583bcc0 0000000000000010
    ffff880244606c88 ffff880244606c20 00000000f3a61725 0000000000000000
    Call Trace:
    <NMI> [<ffffffff9583e9fa>] dump_stack+0x4e/0x7a
    ...

It was easily reproducible by running two or more cores at 100% for a few minutes. I wanted to be a good citizen and report it, but I wasn't able to figure out where or how you're supposed to report kernel bugs. If it's the same bug as the Phoronix article mentions, then it's not a regression because I've had the problem in 3.13 too.