[RFC PATCH 02/21] list: Remove hlist_nulls_unhashed_lockless()

[Will Deacon]

Commit 02b99b38f3d9 ("rcu: Add a hlist_nulls_unhashed_lockless() function")
introduced the (as yet unused) hlist_nulls_unhashed_lockless() function
to avoid KCSAN reports when an RCU reader checks the 'hashed' status
of an 'hlist_nulls' concurrently undergoing modification.

Remove the unused function and add a READ_ONCE() to hlist_nulls_unhashed(),
just like we do already for hlist_nulls_empty().

Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
 include/linux/list_nulls.h | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h
index fa6e8471bd22..3a9ff01e9a11 100644
--- a/include/linux/list_nulls.h
+++ b/include/linux/list_nulls.h
@@ -65,20 +65,6 @@ static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr)
  * but hlist_nulls_del() does not.
  */
 static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h)
-{
-	return !h->pprev;
-}
-
-/**
- * hlist_nulls_unhashed_lockless - Has node been removed and reinitialized?
- * @h: Node to be checked
- *
- * Not that not all removal functions will leave a node in unhashed state.
- * For example, hlist_del_init_rcu() leaves the node in unhashed state,
- * but hlist_nulls_del() does not.  Unlike hlist_nulls_unhashed(), this
- * function may be used locklessly.
- */
-static inline int hlist_nulls_unhashed_lockless(const struct hlist_nulls_node *h)
 {
 	return !READ_ONCE(h->pprev);
 }
-- 
2.20.1