Commit d186204a authored by SeongJae Park's avatar SeongJae Park Committed by Paul E. McKenney
Browse files

Docs/RCU/rculist_nulls: Fix hlist_[nulls]_head field names of 'obj' 



The example code snippets on rculist_nulls.rst are assuming 'obj' to
have the 'hlist_head' or 'hlist_nulls_head' field named 'obj_node', but
a sentence and some code snippets are wrongly calling
'obj->obj_node.next' as 'obj->obj_next', or 'obj->obj_node' as 'member'.
Fix it.

Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 5326caa7

Documentation/RCU/rculist_nulls.rst

+4 −4
Original line number Diff line number Diff line
@@ -65,7 +65,7 @@ but a version with an additional memory barrier (smp_rmb()) 
    struct hlist_node *node, *next;

    for (pos = rcu_dereference((head)->first);

         pos && ({ next = pos->next; smp_rmb(); prefetch(next); 1; }) &&

         ({ obj = hlist_entry(pos, typeof(*obj), member); 1; });

         ({ obj = hlist_entry(pos, typeof(*obj), obj_node); 1; });

         pos = rcu_dereference(next))

      if (obj->key == key)

        return obj;
@@ -77,7 +77,7 @@ And note the traditional hlist_for_each_entry_rcu() misses this smp_rmb():: 
  struct hlist_node *node;

  for (pos = rcu_dereference((head)->first);

       pos && ({ prefetch(pos->next); 1; }) &&

       ({ obj = hlist_entry(pos, typeof(*obj), member); 1; });

       ({ obj = hlist_entry(pos, typeof(*obj), obj_node); 1; });

       pos = rcu_dereference(pos->next))

    if (obj->key == key)

      return obj;
@@ -97,7 +97,7 @@ Quoting Corey Minyard:: 
2) Insertion algorithm

----------------------



We need to make sure a reader cannot read the new 'obj->obj_next' value

We need to make sure a reader cannot read the new 'obj->obj_node.next' value

and previous value of 'obj->key'. Otherwise, an item could be deleted

from a chain, and inserted into another chain. If new chain was empty

before the move, 'next' pointer is NULL, and lockless reader can not
@@ -165,7 +165,7 @@ Note that using hlist_nulls means the type of 'obj_node' field of 
  head = &table[slot];

  begin:

  rcu_read_lock();

  hlist_nulls_for_each_entry_rcu(obj, node, head, member) {

  hlist_nulls_for_each_entry_rcu(obj, node, head, obj_node) {

    if (obj->key == key) {

      if (!try_get_ref(obj)) { // might fail for free objects

	rcu_read_unlock();