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locking/atomics: COCCINELLE/treewide: Convert trivial ACCESS_ONCE() patterns to READ_ONCE()/WRITE_ONCE()

Browse source 
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>
This commit is contained in:
Mark Rutland 2017-10-23 14:07:29 -07:00 • committed by Ingo Molnar
parent b03a0fe0c5
commit 6aa7de0591
180 changed files with 383 additions and 385 deletions
Download patch file Download diff file Expand all files Collapse all files

20
lib/assoc_array.c
View file

@ -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