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>

1 files changed, 4 insertions, 6 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 8bf89267dc25..ccf52368a073 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -734,7 +734,7 @@ static unsigned int ar_search_last_active_buffer(struct ar_context *ctx,
 	__le16 res_count, next_res_count;
 
 	i = ar_first_buffer_index(ctx);
-	res_count = ACCESS_ONCE(ctx->descriptors[i].res_count);
+	res_count = READ_ONCE(ctx->descriptors[i].res_count);
 
 	/* A buffer that is not yet completely filled must be the last one. */
 	while (i != last && res_count == 0) {
@@ -742,8 +742,7 @@ static unsigned int ar_search_last_active_buffer(struct ar_context *ctx,
 		/* Peek at the next descriptor. */
 		next_i = ar_next_buffer_index(i);
 		rmb(); /* read descriptors in order */
-		next_res_count = ACCESS_ONCE(
-				ctx->descriptors[next_i].res_count);
+		next_res_count = READ_ONCE(ctx->descriptors[next_i].res_count);
 		/*
 		 * If the next descriptor is still empty, we must stop at this
 		 * descriptor.
@@ -759,8 +758,7 @@ static unsigned int ar_search_last_active_buffer(struct ar_context *ctx,
 			if (MAX_AR_PACKET_SIZE > PAGE_SIZE && i != last) {
 				next_i = ar_next_buffer_index(next_i);
 				rmb();
-				next_res_count = ACCESS_ONCE(
-					ctx->descriptors[next_i].res_count);
+				next_res_count = READ_ONCE(ctx->descriptors[next_i].res_count);
 				if (next_res_count != cpu_to_le16(PAGE_SIZE))
 					goto next_buffer_is_active;
 			}
@@ -2812,7 +2810,7 @@ static int handle_ir_buffer_fill(struct context *context,
 	u32 buffer_dma;
 
 	req_count = le16_to_cpu(last->req_count);
-	res_count = le16_to_cpu(ACCESS_ONCE(last->res_count));
+	res_count = le16_to_cpu(READ_ONCE(last->res_count));
 	completed = req_count - res_count;
 	buffer_dma = le32_to_cpu(last->data_address);