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>

3 files changed, 3 insertions, 3 deletions

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 81279c6602ff..845f3805c73d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2724,7 +2724,7 @@ rb_reserve_next_event(struct ring_buffer *buffer,
 	 * if it happened, we have to fail the write.
 	 */
 	barrier();
-	if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
+	if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
 		local_dec(&cpu_buffer->committing);
 		local_dec(&cpu_buffer->commits);
 		return NULL;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 652c682707cd..9050c8b3ccde 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1459,7 +1459,7 @@ extern struct trace_event_file *find_event_file(struct trace_array *tr,
 
 static inline void *event_file_data(struct file *filp)
 {
-	return ACCESS_ONCE(file_inode(filp)->i_private);
+	return READ_ONCE(file_inode(filp)->i_private);
 }
 
 extern struct mutex event_mutex;
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 49cb41412eec..780262210c9a 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -77,7 +77,7 @@ check_stack(unsigned long ip, unsigned long *stack)
 {
 	unsigned long this_size, flags; unsigned long *p, *top, *start;
 	static int tracer_frame;
-	int frame_size = ACCESS_ONCE(tracer_frame);
+	int frame_size = READ_ONCE(tracer_frame);
 	int i, x;
 
 	this_size = ((unsigned long)stack) & (THREAD_SIZE-1);