rcu-tasks: Document that RCU Tasks Trace grace periods now imply RCU grace periods

Now that RCU Tasks Trace is implemented in terms of SRCU-fast, the fact
that each SRCU-fast grace period implies at least two RCU grace periods
in turn means that each RCU Tasks Trace grace period implies at least
two grace periods.  This commit therefore updates the documentation
accordingly.

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>

1 files changed, 3 insertions, 6 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 04f3f86a4145..18a85c30fd4f 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -208,12 +208,9 @@ static inline void exit_tasks_rcu_finish(void) { }
 /**
  * rcu_trace_implies_rcu_gp - does an RCU Tasks Trace grace period imply an RCU grace period?
  *
- * As an accident of implementation, an RCU Tasks Trace grace period also
- * acts as an RCU grace period.  However, this could change at any time.
- * Code relying on this accident must call this function to verify that
- * this accident is still happening.
- *
- * You have been warned!
+ * Now that RCU Tasks Trace is implemented in terms of SRCU-fast, a
+ * call to synchronize_rcu_tasks_trace() is guaranteed to imply at least
+ * one call to synchronize_rcu().
  */
 static inline bool rcu_trace_implies_rcu_gp(void) { return true; }