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, 6 insertions, 6 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index 8a32a8f7f9c0..3541a7f9d12e 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -414,8 +414,8 @@ bool mlx4_en_process_tx_cq(struct net_device *dev,
 
 	index = cons_index & size_mask;
 	cqe = mlx4_en_get_cqe(buf, index, priv->cqe_size) + factor;
-	last_nr_txbb = ACCESS_ONCE(ring->last_nr_txbb);
-	ring_cons = ACCESS_ONCE(ring->cons);
+	last_nr_txbb = READ_ONCE(ring->last_nr_txbb);
+	ring_cons = READ_ONCE(ring->cons);
 	ring_index = ring_cons & size_mask;
 	stamp_index = ring_index;
 
@@ -479,8 +479,8 @@ bool mlx4_en_process_tx_cq(struct net_device *dev,
 	wmb();
 
 	/* we want to dirty this cache line once */
-	ACCESS_ONCE(ring->last_nr_txbb) = last_nr_txbb;
-	ACCESS_ONCE(ring->cons) = ring_cons + txbbs_skipped;
+	WRITE_ONCE(ring->last_nr_txbb, last_nr_txbb);
+	WRITE_ONCE(ring->cons, ring_cons + txbbs_skipped);
 
 	if (cq->type == TX_XDP)
 		return done < budget;
@@ -858,7 +858,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto tx_drop;
 
 	/* fetch ring->cons far ahead before needing it to avoid stall */
-	ring_cons = ACCESS_ONCE(ring->cons);
+	ring_cons = READ_ONCE(ring->cons);
 
 	real_size = get_real_size(skb, shinfo, dev, &lso_header_size,
 				  &inline_ok, &fragptr);
@@ -1066,7 +1066,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		 */
 		smp_rmb();
 
-		ring_cons = ACCESS_ONCE(ring->cons);
+		ring_cons = READ_ONCE(ring->cons);
 		if (unlikely(!mlx4_en_is_tx_ring_full(ring))) {
 			netif_tx_wake_queue(ring->tx_queue);
 			ring->wake_queue++;