On 07/17/2012 12:05 AM, John Stultz wrote:
> 1) Deadlock leapsecond issue that a few reports described.
>
> I spent some time over the weekend trying to find a way to reproduce
> the hard-hang issue some folks were reporting after the leapsecond.
> Initially I didn't think the 6b43ae8a619d17 leap-second hrimter livelock
> patch needed to be backported since, I assumed it required the ntp_lock
> split for it to be triggered, but looking again I found that the same
> issue could occur prior to splitting out the ntp_lock. So I've backported
> that fix (and its follow-on fixups) as well as created a test case
> to reproduce the hard-hang deadlock.

Attached is the test case I used to reproduce and test the solution to 
the hard-hang deadlock.

WARNING: THIS TEST WILL LIKELY HARD LOCK YOUR BOX IN IRQ CONTEXT!
YOU MAY LOSE DATA! RUN AT YOUR OWN RISK!

thanks
-john