Now that smp_read_barrier_depends() is implied by READ_ONCE(), adding
READ_ONCE() to assoc_array_ptr_to_leaf() and __assoc_array_ptr_to_meta()
allows the several smp_read_barrier_depends() calls to be removed from
lib/assoc_array.c. This commit makes this change.
Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Jonathan Corbet <cor...@lwn.net>
Cc: Mark Rutland <mark.rutl...@arm.com>
Cc: Alexander Kuleshov <kuleshovm...@gmail.com>
---
include/linux/assoc_array_priv.h | 5 +++--
lib/assoc_array.c | 20 ++------------------
2 files changed, 5 insertions(+), 20 deletions(-)
diff --git a/include/linux/assoc_array_priv.h b/include/linux/assoc_array_priv.h
index 711275e6681c..b47308bf1f99 100644
--- a/include/linux/assoc_array_priv.h
+++ b/include/linux/assoc_array_priv.h
@@ -135,13 +135,14 @@ static inline bool assoc_array_ptr_is_node(const struct
assoc_array_ptr *x)
static inline void *assoc_array_ptr_to_leaf(const struct assoc_array_ptr *x)
{
- return (void *)((unsigned long)x & ~ASSOC_ARRAY_PTR_TYPE_MASK);
+ return (void *)((unsigned long)READ_ONCE(x) & /* Address dependency. */
+ ~ASSOC_ARRAY_PTR_TYPE_MASK);
}
static inline
unsigned long __assoc_array_ptr_to_meta(const struct assoc_array_ptr *x)
{
- return (unsigned long)x &
+ return (unsigned long)READ_ONCE(x) & /* Address dependency. */
~(ASSOC_ARRAY_PTR_SUBTYPE_MASK | ASSOC_ARRAY_PTR_TYPE_MASK);
}
static inline
diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index fe7953aead82..52845f5cbf19 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -38,12 +38,10 @@ static int assoc_array_subtree_iterate(const struct
assoc_array_ptr *root,
if (assoc_array_ptr_is_shortcut(cursor)) {
/* Descend through a shortcut */
shortcut = assoc_array_ptr_to_shortcut(cursor);
- smp_read_barrier_depends();
cursor = READ_ONCE(shortcut->next_node);
}
node = assoc_array_ptr_to_node(cursor);
- smp_read_barrier_depends();
slot = 0;
/* We perform two passes of each node.
@@ -55,15 +53,9 @@ static int assoc_array_subtree_iterate(const struct
assoc_array_ptr *root,
*/
has_meta = 0;
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
- ptr = READ_ONCE(node->slots[slot]);
+ ptr = READ_ONCE(node->slots[slot]); /* Address dependency. */
has_meta |= (unsigned long)ptr;
if (ptr && assoc_array_ptr_is_leaf(ptr)) {
- /* We need a barrier between the read of the pointer
- * and dereferencing the pointer - but only if we are
- * actually going to dereference it.
- */
- smp_read_barrier_depends();
-
/* Invoke the callback */
ret = iterator(assoc_array_ptr_to_leaf(ptr),
iterator_data);
@@ -86,8 +78,6 @@ static int assoc_array_subtree_iterate(const struct
assoc_array_ptr *root,
continue_node:
node = assoc_array_ptr_to_node(cursor);
- smp_read_barrier_depends();
-
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
ptr = READ_ONCE(node->slots[slot]);
if (assoc_array_ptr_is_meta(ptr)) {
@@ -105,7 +95,6 @@ static int assoc_array_subtree_iterate(const struct
assoc_array_ptr *root,
if (assoc_array_ptr_is_shortcut(parent)) {
shortcut = assoc_array_ptr_to_shortcut(parent);
- smp_read_barrier_depends();
cursor = parent;
parent = READ_ONCE(shortcut->back_pointer);
slot = shortcut->parent_slot;
@@ -216,8 +205,6 @@ assoc_array_walk(const struct assoc_array *array,
consider_node:
node = assoc_array_ptr_to_node(cursor);
- smp_read_barrier_depends();
-
slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
slot &= ASSOC_ARRAY_FAN_MASK;
ptr = READ_ONCE(node->slots[slot]);
@@ -254,7 +241,6 @@ assoc_array_walk(const struct assoc_array *array,
cursor = ptr;
follow_shortcut:
shortcut = assoc_array_ptr_to_shortcut(cursor);
- smp_read_barrier_depends();
pr_devel("shortcut to %d\n", shortcut->skip_to_level);
sc_level = level + ASSOC_ARRAY_LEVEL_STEP;
BUG_ON(sc_level > shortcut->skip_to_level);
@@ -330,8 +316,7 @@ void *assoc_array_find(const struct assoc_array *array,
assoc_array_walk_found_terminal_node)
return NULL;
- node = result.terminal_node.node;
- smp_read_barrier_depends();
+ node = READ_ONCE(result.terminal_node.node); /* Address dependency. */
/* If the target key is available to us, it's has to be pointed to by
* the terminal node.
@@ -344,7 +329,6 @@ void *assoc_array_find(const struct assoc_array *array,
* actually going to dereference it.
*/
leaf = assoc_array_ptr_to_leaf(ptr);
- smp_read_barrier_depends();
if (ops->compare_object(leaf, index_key))
return (void *)leaf;
}
--
2.5.2
