rcu-tasks: Add block comment laying out RCU Rude design

This commit adds a block comment that gives a high-level overview of
how RCU Rude grace periods progress.  It also gives an overview of the
memory ordering.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2021-03-04 14:46:59 -08:00
commit 9fc98e3143