Document grace period polling in rcu-api.md

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I74631072d19cbe1212be6d1ab4f08778d59f67dd

diff --git a/doc/rcu-api.md b/doc/rcu-api.md
index e8ec0228731361b17d558f1236c6e61dea63ad05..4163eefb287a9f7f934fa6642246a2061c570471 100644 (file)
--- a/doc/rcu-api.md
+++ b/doc/rcu-api.md
@@ -60,6 +60,26 @@ started: this is not a reader-writer lock. The duration
 actually waited is called an RCU grace period.
 
 
+```c
+struct urcu_gp_poll_state start_poll_synchronize_rcu(void);
+```
+
+Start polling on grace period. The returned poll state should be
+queried using `poll_state_synchronize_rcu` to check whether the
+grace period has completed.
+
+`start_poll_synchronize_rcu` should be called from registered RCU
+read-side threads.  For the QSBR flavor, the caller should be online.
+
+
+```c
+bool poll_state_synchronize_rcu(struct urcu_gp_poll_state state);
+```
+
+Poll the grace period state. Return true if quiescence was reached since
+the grace period was started, return false otherwise.
+
+
 ```c
 void call_rcu(struct rcu_head *head,
               void (*func)(struct rcu_head *head));