locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()
Please do not apply this to mainline directly, instead please re-run the
coccinelle script shown below and apply its output.
For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't harmful, and changing them results in
churn.
However, for some features, the read/write distinction is critical to
correct operation. To distinguish these cases, separate read/write
accessors must be used. This patch migrates (most) remaining
ACCESS_ONCE() instances to {READ,WRITE}_ONCE(), using the following
coccinelle script:
----
// Convert trivial ACCESS_ONCE() uses to equivalent READ_ONCE() and
// WRITE_ONCE()
// $ make coccicheck COCCI=/home/mark/once.cocci SPFLAGS="--include-headers" MODE=patch
virtual patch
@ depends on patch @
expression E1, E2;
@@
- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)
@ depends on patch @
expression E;
@@
- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-19-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index 155c55d..fe7953a 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -39,7 +39,7 @@ static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
/* Descend through a shortcut */
shortcut = assoc_array_ptr_to_shortcut(cursor);
smp_read_barrier_depends();
- cursor = ACCESS_ONCE(shortcut->next_node);
+ cursor = READ_ONCE(shortcut->next_node);
}
node = assoc_array_ptr_to_node(cursor);
@@ -55,7 +55,7 @@ static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
*/
has_meta = 0;
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
- ptr = ACCESS_ONCE(node->slots[slot]);
+ ptr = READ_ONCE(node->slots[slot]);
has_meta |= (unsigned long)ptr;
if (ptr && assoc_array_ptr_is_leaf(ptr)) {
/* We need a barrier between the read of the pointer
@@ -89,7 +89,7 @@ static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
smp_read_barrier_depends();
for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
- ptr = ACCESS_ONCE(node->slots[slot]);
+ ptr = READ_ONCE(node->slots[slot]);
if (assoc_array_ptr_is_meta(ptr)) {
cursor = ptr;
goto begin_node;
@@ -98,7 +98,7 @@ static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
finished_node:
/* Move up to the parent (may need to skip back over a shortcut) */
- parent = ACCESS_ONCE(node->back_pointer);
+ parent = READ_ONCE(node->back_pointer);
slot = node->parent_slot;
if (parent == stop)
return 0;
@@ -107,7 +107,7 @@ static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root,
shortcut = assoc_array_ptr_to_shortcut(parent);
smp_read_barrier_depends();
cursor = parent;
- parent = ACCESS_ONCE(shortcut->back_pointer);
+ parent = READ_ONCE(shortcut->back_pointer);
slot = shortcut->parent_slot;
if (parent == stop)
return 0;
@@ -147,7 +147,7 @@ int assoc_array_iterate(const struct assoc_array *array,
void *iterator_data),
void *iterator_data)
{
- struct assoc_array_ptr *root = ACCESS_ONCE(array->root);
+ struct assoc_array_ptr *root = READ_ONCE(array->root);
if (!root)
return 0;
@@ -194,7 +194,7 @@ assoc_array_walk(const struct assoc_array *array,
pr_devel("-->%s()\n", __func__);
- cursor = ACCESS_ONCE(array->root);
+ cursor = READ_ONCE(array->root);
if (!cursor)
return assoc_array_walk_tree_empty;
@@ -220,7 +220,7 @@ assoc_array_walk(const struct assoc_array *array,
slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
slot &= ASSOC_ARRAY_FAN_MASK;
- ptr = ACCESS_ONCE(node->slots[slot]);
+ ptr = READ_ONCE(node->slots[slot]);
pr_devel("consider slot %x [ix=%d type=%lu]\n",
slot, level, (unsigned long)ptr & 3);
@@ -294,7 +294,7 @@ assoc_array_walk(const struct assoc_array *array,
} while (sc_level < shortcut->skip_to_level);
/* The shortcut matches the leaf's index to this point. */
- cursor = ACCESS_ONCE(shortcut->next_node);
+ cursor = READ_ONCE(shortcut->next_node);
if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) {
level = sc_level;
goto jumped;
@@ -337,7 +337,7 @@ void *assoc_array_find(const struct assoc_array *array,
* the terminal node.
*/
for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
- ptr = ACCESS_ONCE(node->slots[slot]);
+ ptr = READ_ONCE(node->slots[slot]);
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