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>

sound/firewire/fireface/amdtp-ff.c

@@ -108,7 +108,7 @@ static unsigned int process_rx_data_blocks(struct amdtp_stream *s,
 					   unsigned int data_blocks,
 					   unsigned int *syt)
 {
-	struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);
+	struct snd_pcm_substream *pcm = READ_ONCE(s->pcm);
 	unsigned int pcm_frames;
 
 	if (pcm) {
@@ -127,7 +127,7 @@ static unsigned int process_tx_data_blocks(struct amdtp_stream *s,
 					   unsigned int data_blocks,
 					   unsigned int *syt)
 {
-	struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);
+	struct snd_pcm_substream *pcm = READ_ONCE(s->pcm);
 	unsigned int pcm_frames;
 
 	if (pcm) {

sound/firewire/fireface/ff-midi.c

@@ -22,7 +22,7 @@ static int midi_playback_open(struct snd_rawmidi_substream *substream)
 	ff->running_status[substream->number] = 0;
 	ff->rx_midi_error[substream->number] = false;
 
-	ACCESS_ONCE(ff->rx_midi_substreams[substream->number]) = substream;
+	WRITE_ONCE(ff->rx_midi_substreams[substream->number], substream);
 
 	return 0;
 }
@@ -38,7 +38,7 @@ static int midi_playback_close(struct snd_rawmidi_substream *substream)
 	struct snd_ff *ff = substream->rmidi->private_data;
 
 	cancel_work_sync(&ff->rx_midi_work[substream->number]);
-	ACCESS_ONCE(ff->rx_midi_substreams[substream->number]) = NULL;
+	WRITE_ONCE(ff->rx_midi_substreams[substream->number], NULL);
 
 	return 0;
 }
@@ -52,10 +52,10 @@ static void midi_capture_trigger(struct snd_rawmidi_substream *substream,
 	spin_lock_irqsave(&ff->lock, flags);
 
 	if (up)
-		ACCESS_ONCE(ff->tx_midi_substreams[substream->number]) =
-								substream;
+		WRITE_ONCE(ff->tx_midi_substreams[substream->number],
+			   substream);
 	else
-		ACCESS_ONCE(ff->tx_midi_substreams[substream->number]) = NULL;
+		WRITE_ONCE(ff->tx_midi_substreams[substream->number], NULL);
 
 	spin_unlock_irqrestore(&ff->lock, flags);
 }

sound/firewire/fireface/ff-transaction.c

@@ -12,7 +12,7 @@ static void finish_transmit_midi_msg(struct snd_ff *ff, unsigned int port,
 				     int rcode)
 {
 	struct snd_rawmidi_substream *substream =
-				ACCESS_ONCE(ff->rx_midi_substreams[port]);
+				READ_ONCE(ff->rx_midi_substreams[port]);
 
 	if (rcode_is_permanent_error(rcode)) {
 		ff->rx_midi_error[port] = true;
@@ -60,7 +60,7 @@ static inline void fill_midi_buf(struct snd_ff *ff, unsigned int port,
 static void transmit_midi_msg(struct snd_ff *ff, unsigned int port)
 {
 	struct snd_rawmidi_substream *substream =
-			ACCESS_ONCE(ff->rx_midi_substreams[port]);
+			READ_ONCE(ff->rx_midi_substreams[port]);
 	u8 *buf = (u8 *)ff->msg_buf[port];
 	int i, len;
 
@@ -159,7 +159,7 @@ static void handle_midi_msg(struct fw_card *card, struct fw_request *request,
 		 */
 		index = (quad >> 8) & 0xff;
 		if (index > 0) {
-			substream = ACCESS_ONCE(ff->tx_midi_substreams[0]);
+			substream = READ_ONCE(ff->tx_midi_substreams[0]);
 			if (substream != NULL) {
 				byte = quad & 0xff;
 				snd_rawmidi_receive(substream, &byte, 1);
@@ -169,7 +169,7 @@ static void handle_midi_msg(struct fw_card *card, struct fw_request *request,
 		/* Message in second port. */
 		index = (quad >> 24) & 0xff;
 		if (index > 0) {
-			substream = ACCESS_ONCE(ff->tx_midi_substreams[1]);
+			substream = READ_ONCE(ff->tx_midi_substreams[1]);
 			if (substream != NULL) {
 				byte = (quad >> 16) & 0xff;
 				snd_rawmidi_receive(substream, &byte, 1);