On Thu, 11 Aug 2016, Paul E. McKenney wrote:

quoted

With modern Intel we could run it on one CPU per package I think, but at
the same time, too much in NOHZ_FULL assumes the TSC is indeed sane so
it doesn't make sense to me to keep the watchdog running, when it
triggers it would also have to kill all NOHZ_FULL stuff, which would
probably bring the entire machine down..

Well, you -could- force a very low priority CPU-bound task to run on
all nohz_full CPUs.  Not necessarily a good idea, but a relatively
non-intrusive response to that particular error condition.

Given that we want the cpu only to run the user task I would think that is
not a good idea.