Merge branch 'rcu/misc' into next

Merge branch 'rcu/misc' into next

- In order to prepare the layout for nohz_full work deferral to
  user exit, the context tracking state must shrink the counter
  of transitions to/from RCU not watching. The only possible hazard
  is to trigger wrap-around more easily, delaying a bit grace periods
  when that happens. This should be a rare event though. Yet add
  debugging and torture code to test that assumption.

- Fix memory leak on locktorture module

- Annotate accesses in rculist_nulls.h to prevent from KCSAN warnings.
  On recent discussions, we also concluded that all those WRITE_ONCE()
  and READ_ONCE() on list APIs deserve appropriate comments. Something
  to be expected for the next cycle.

- Provide a script to apply several configs to several commits with torture.

- Allow torture to reuse a build directory in order to save needless
  rebuild time.

- Various cleanups.