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>

4 files changed, 14 insertions, 14 deletions

diff --git a/lib/assoc_array.c b/lib/assoc_array.c
index 155c55d8db5f..fe7953aead82 100644
--- a/lib/assoc_array.c
+++ b/lib/assoc_array.c
@@ -39,7 +39,7 @@ begin_node:
 		/* 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 @@ begin_node:
 	 */
 	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 @@ continue_node:
 	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 @@ continue_node:
 
 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 @@ finished_node:
 		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 @@ consider_node:
 
 	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 @@ follow_shortcut:
 	} 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
diff --git a/lib/dynamic_queue_limits.c b/lib/dynamic_queue_limits.c
index f346715e2255..81770a55cb16 100644
--- a/lib/dynamic_queue_limits.c
+++ b/lib/dynamic_queue_limits.c
@@ -20,7 +20,7 @@ void dql_completed(struct dql *dql, unsigned int count)
 	unsigned int ovlimit, completed, num_queued;
 	bool all_prev_completed;
 
-	num_queued = ACCESS_ONCE(dql->num_queued);
+	num_queued = READ_ONCE(dql->num_queued);
 
 	/* Can't complete more than what's in queue */
 	BUG_ON(count > num_queued - dql->num_completed);
diff --git a/lib/llist.c b/lib/llist.c
index ae5872b1df0c..7062e931a7bb 100644
--- a/lib/llist.c
+++ b/lib/llist.c
@@ -41,7 +41,7 @@ bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
 	struct llist_node *first;
 
 	do {
-		new_last->next = first = ACCESS_ONCE(head->first);
+		new_last->next = first = READ_ONCE(head->first);
 	} while (cmpxchg(&head->first, first, new_first) != first);
 
 	return !first;
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 86c3385b9eb3..1746bae94d41 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -620,8 +620,8 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp
 
 	rcu_read_lock();
 	for (i = 0; i < depth; i++, d = p) {
-		p = ACCESS_ONCE(d->d_parent);
-		array[i] = ACCESS_ONCE(d->d_name.name);
+		p = READ_ONCE(d->d_parent);
+		array[i] = READ_ONCE(d->d_name.name);
 		if (p == d) {
 			if (i)
 				array[i] = "";