[PATCH v4 1/3] Docs/RCU/rculist_nulls: Specify type of the object in examples

[SeongJae Park]

The type of 'obj' in example code of rculist_nulls.rst is implicit.
Provide the specific type of it before the example code.

Suggested-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Link: https://lore.kernel.org/rcu/43943609-f80c-4b6a-9844-994eef800757@paulmck-laptop/
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 Documentation/RCU/rculist_nulls.rst | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Documentation/RCU/rculist_nulls.rst b/Documentation/RCU/rculist_nulls.rst
index 94a8bfe9f560..a6827cc31791 100644
--- a/Documentation/RCU/rculist_nulls.rst
+++ b/Documentation/RCU/rculist_nulls.rst
@@ -18,7 +18,16 @@ to solve following problem.
 
 Without 'nulls', a typical RCU linked list managing objects which are
 allocated with SLAB_TYPESAFE_BY_RCU kmem_cache can use the following
-algorithms:
+algorithms.  Following examples assume 'obj' is a pointer to such
+objects, which is having below type.
+
+::
+
+  struct object {
+    struct hlist_node obj_node;
+    atomic_t refcnt;
+    unsigned int key;
+  };
 
 1) Lookup algorithm
 -------------------
@@ -142,6 +151,9 @@ the beginning. If the object was moved to the same chain,
 then the reader doesn't care: It might occasionally
 scan the list again without harm.
 
+Note that using hlist_nulls means the type of 'obj_node' field of
+'struct object' becomes 'struct hlist_nulls_node'.
+
 
 1) lookup algorithm
 -------------------
-- 
2.25.1