On Wed, Sep 29, 2021 at 11:37:01AM -0700, Paul E. McKenney wrote:

And what happens to all of this in !CONFIG_CONTEXT_TRACKING kernels?
Of course, RCU needs it unconditionally.  (There appear to be at least
parts of it that are unconditionally available, but I figured that I
should ask.  Especially given the !CONFIG_CONTEXT_TRACKING definition
of the __context_tracking_cpu_seq() function.)

For !CONFIG_CONTEXT_TRACKING it goes *poof*.

Since the thing was called dynticks, I presumed it was actually dynticks
only, silly me (also, I didn't see any obvious !context_tracking usage
of it, i'll go audit it more carefully.