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>

drivers/infiniband/hw/hfi1/file_ops.c

@@ -380,7 +380,7 @@ static long hfi1_file_ioctl(struct file *fp, unsigned int cmd,
 		if (sc->flags & SCF_FROZEN) {
 			wait_event_interruptible_timeout(
 				dd->event_queue,
-				!(ACCESS_ONCE(dd->flags) & HFI1_FROZEN),
+				!(READ_ONCE(dd->flags) & HFI1_FROZEN),
 				msecs_to_jiffies(SEND_CTXT_HALT_TIMEOUT));
 			if (dd->flags & HFI1_FROZEN)
 				return -ENOLCK;

drivers/infiniband/hw/hfi1/pio.c

@@ -1423,14 +1423,14 @@ retry:
 			goto done;
 		}
 		/* copy from receiver cache line and recalculate */
-		sc->alloc_free = ACCESS_ONCE(sc->free);
+		sc->alloc_free = READ_ONCE(sc->free);
 		avail =
 			(unsigned long)sc->credits -
 			(sc->fill - sc->alloc_free);
 		if (blocks > avail) {
 			/* still no room, actively update */
 			sc_release_update(sc);
-			sc->alloc_free = ACCESS_ONCE(sc->free);
+			sc->alloc_free = READ_ONCE(sc->free);
 			trycount++;
 			goto retry;
 		}
@@ -1667,7 +1667,7 @@ void sc_release_update(struct send_context *sc)
 
 	/* call sent buffer callbacks */
 	code = -1;				/* code not yet set */
-	head = ACCESS_ONCE(sc->sr_head);	/* snapshot the head */
+	head = READ_ONCE(sc->sr_head);	/* snapshot the head */
 	tail = sc->sr_tail;
 	while (head != tail) {
 		pbuf = &sc->sr[tail].pbuf;

drivers/infiniband/hw/hfi1/ruc.c

@@ -363,7 +363,7 @@ static void ruc_loopback(struct rvt_qp *sqp)
 
 again:
 	smp_read_barrier_depends(); /* see post_one_send() */
-	if (sqp->s_last == ACCESS_ONCE(sqp->s_head))
+	if (sqp->s_last == READ_ONCE(sqp->s_head))
 		goto clr_busy;
 	wqe = rvt_get_swqe_ptr(sqp, sqp->s_last);
 

drivers/infiniband/hw/hfi1/sdma.c

@@ -1725,7 +1725,7 @@ retry:
 
 		swhead = sde->descq_head & sde->sdma_mask;
 		/* this code is really bad for cache line trading */
-		swtail = ACCESS_ONCE(sde->descq_tail) & sde->sdma_mask;
+		swtail = READ_ONCE(sde->descq_tail) & sde->sdma_mask;
 		cnt = sde->descq_cnt;
 
 		if (swhead < swtail)
@@ -1872,7 +1872,7 @@ retry:
 	if ((status & sde->idle_mask) && !idle_check_done) {
 		u16 swtail;
 
-		swtail = ACCESS_ONCE(sde->descq_tail) & sde->sdma_mask;
+		swtail = READ_ONCE(sde->descq_tail) & sde->sdma_mask;
 		if (swtail != hwhead) {
 			hwhead = (u16)read_sde_csr(sde, SD(HEAD));
 			idle_check_done = 1;
@@ -2222,7 +2222,7 @@ void sdma_seqfile_dump_sde(struct seq_file *s, struct sdma_engine *sde)
 	u16 len;
 
 	head = sde->descq_head & sde->sdma_mask;
-	tail = ACCESS_ONCE(sde->descq_tail) & sde->sdma_mask;
+	tail = READ_ONCE(sde->descq_tail) & sde->sdma_mask;
 	seq_printf(s, SDE_FMT, sde->this_idx,
 		   sde->cpu,
 		   sdma_state_name(sde->state.current_state),
@@ -3305,7 +3305,7 @@ int sdma_ahg_alloc(struct sdma_engine *sde)
 		return -EINVAL;
 	}
 	while (1) {
-		nr = ffz(ACCESS_ONCE(sde->ahg_bits));
+		nr = ffz(READ_ONCE(sde->ahg_bits));
 		if (nr > 31) {
 			trace_hfi1_ahg_allocate(sde, -ENOSPC);
 			return -ENOSPC;

drivers/infiniband/hw/hfi1/sdma.h

@@ -445,7 +445,7 @@ static inline u16 sdma_descq_freecnt(struct sdma_engine *sde)
 {
 	return sde->descq_cnt -
 		(sde->descq_tail -
-		 ACCESS_ONCE(sde->descq_head)) - 1;
+		 READ_ONCE(sde->descq_head)) - 1;
 }
 
 static inline u16 sdma_descq_inprocess(struct sdma_engine *sde)

drivers/infiniband/hw/hfi1/uc.c

@@ -80,7 +80,7 @@ int hfi1_make_uc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 			goto bail;
 		/* We are in the error state, flush the work request. */
 		smp_read_barrier_depends(); /* see post_one_send() */
-		if (qp->s_last == ACCESS_ONCE(qp->s_head))
+		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
 		if (iowait_sdma_pending(&priv->s_iowait)) {
@@ -121,7 +121,7 @@ int hfi1_make_uc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 			goto bail;
 		/* Check if send work queue is empty. */
 		smp_read_barrier_depends(); /* see post_one_send() */
-		if (qp->s_cur == ACCESS_ONCE(qp->s_head)) {
+		if (qp->s_cur == READ_ONCE(qp->s_head)) {
 			clear_ahg(qp);
 			goto bail;
 		}

drivers/infiniband/hw/hfi1/ud.c

@@ -487,7 +487,7 @@ int hfi1_make_ud_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 			goto bail;
 		/* We are in the error state, flush the work request. */
 		smp_read_barrier_depends(); /* see post_one_send */
-		if (qp->s_last == ACCESS_ONCE(qp->s_head))
+		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
 		if (iowait_sdma_pending(&priv->s_iowait)) {
@@ -501,7 +501,7 @@ int hfi1_make_ud_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 
 	/* see post_one_send() */
 	smp_read_barrier_depends();
-	if (qp->s_cur == ACCESS_ONCE(qp->s_head))
+	if (qp->s_cur == READ_ONCE(qp->s_head))
 		goto bail;
 
 	wqe = rvt_get_swqe_ptr(qp, qp->s_cur);

drivers/infiniband/hw/hfi1/user_sdma.c

@@ -276,7 +276,7 @@ int hfi1_user_sdma_free_queues(struct hfi1_filedata *fd,
 		/* Wait until all requests have been freed. */
 		wait_event_interruptible(
 			pq->wait,
-			(ACCESS_ONCE(pq->state) == SDMA_PKT_Q_INACTIVE));
+			(READ_ONCE(pq->state) == SDMA_PKT_Q_INACTIVE));
 		kfree(pq->reqs);
 		kfree(pq->req_in_use);
 		kmem_cache_destroy(pq->txreq_cache);
@@ -591,7 +591,7 @@ int hfi1_user_sdma_process_request(struct hfi1_filedata *fd,
 			if (ret != -EBUSY) {
 				req->status = ret;
 				WRITE_ONCE(req->has_error, 1);
-				if (ACCESS_ONCE(req->seqcomp) ==
+				if (READ_ONCE(req->seqcomp) ==
 				    req->seqsubmitted - 1)
 					goto free_req;
 				return ret;
@@ -825,7 +825,7 @@ static int user_sdma_send_pkts(struct user_sdma_request *req, unsigned maxpkts)
 		 */
 		if (req->data_len) {
 			iovec = &req->iovs[req->iov_idx];
-			if (ACCESS_ONCE(iovec->offset) == iovec->iov.iov_len) {
+			if (READ_ONCE(iovec->offset) == iovec->iov.iov_len) {
 				if (++req->iov_idx == req->data_iovs) {
 					ret = -EFAULT;
 					goto free_txreq;
@@ -1390,7 +1390,7 @@ static void user_sdma_txreq_cb(struct sdma_txreq *txreq, int status)
 	} else {
 		if (status != SDMA_TXREQ_S_OK)
 			req->status = status;
-		if (req->seqcomp == (ACCESS_ONCE(req->seqsubmitted) - 1) &&
+		if (req->seqcomp == (READ_ONCE(req->seqsubmitted) - 1) &&
 		    (READ_ONCE(req->done) ||
 		     READ_ONCE(req->has_error))) {
 			user_sdma_free_request(req, false);