drivers/infiniband: Remove now-redundant smp_read_barrier_depends()

The smp_read_barrier_depends() does nothing at all except on DEC Alpha,
and no current DEC Alpha systems use Infiniband:

	lkml.kernel.org/r/20171023085921.jwbntptn6ictbnvj@tower

This commit therefore makes Infiniband depend on !ALPHA and removes
the now-ineffective invocations of smp_read_barrier_depends() from
the InfiniBand driver.

Please note that this patch should not be construed as my saying that
InfiniBand's memory ordering is correct, but rather that this patch does
not in any way affect InfiniBand's correctness.  In other words, the
result of applying this patch is bug-for-bug compatible with the original.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: <linux-rdma@vger.kernel.org>
Cc: <linux-alpha@vger.kernel.org>
[ paulmck: Removed drivers/dma/ioat/dma.c per Jason Gunthorpe's feedback. ]
Acked-by: NJason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/Kconfig

@@ -4,6 +4,7 @@ menuconfig INFINIBAND
 	depends on NET
 	depends on INET
 	depends on m || IPV6 != m
+	depends on !ALPHA
 	select IRQ_POLL
 	---help---
 	  Core support for InfiniBand (IB).  Make sure to also select

drivers/infiniband/hw/hfi1/rc.c

@@ -302,7 +302,6 @@ int hfi1_make_rc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		smp_read_barrier_depends(); /* see post_one_send() */
 		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
@@ -346,7 +345,6 @@ int hfi1_make_rc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 		newreq = 0;
 		if (qp->s_cur == qp->s_tail) {
 			/* Check if send work queue is empty. */
-			smp_read_barrier_depends(); /* see post_one_send() */
 			if (qp->s_tail == READ_ONCE(qp->s_head)) {
 				clear_ahg(qp);
 				goto bail;
@@ -900,7 +898,6 @@ void hfi1_send_rc_ack(struct hfi1_ctxtdata *rcd,
 	}
 
 	/* Ensure s_rdma_ack_cnt changes are committed */
-	smp_read_barrier_depends();
 	if (qp->s_rdma_ack_cnt) {
 		hfi1_queue_rc_ack(qp, is_fecn);
 		return;
@@ -1562,7 +1559,6 @@ static void rc_rcv_resp(struct hfi1_packet *packet)
 	trace_hfi1_ack(qp, psn);
 
 	/* Ignore invalid responses. */
-	smp_read_barrier_depends(); /* see post_one_send */
 	if (cmp_psn(psn, READ_ONCE(qp->s_next_psn)) >= 0)
 		goto ack_done;
 

drivers/infiniband/hw/hfi1/ruc.c

@@ -362,7 +362,6 @@ static void ruc_loopback(struct rvt_qp *sqp)
 	sqp->s_flags |= RVT_S_BUSY;
 
 again:
-	smp_read_barrier_depends(); /* see post_one_send() */
 	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

@@ -553,7 +553,6 @@ static void sdma_hw_clean_up_task(unsigned long opaque)
 
 static inline struct sdma_txreq *get_txhead(struct sdma_engine *sde)
 {
-	smp_read_barrier_depends(); /* see sdma_update_tail() */
 	return sde->tx_ring[sde->tx_head & sde->sdma_mask];
 }
 

drivers/infiniband/hw/hfi1/uc.c

@@ -79,7 +79,6 @@ int hfi1_make_uc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		smp_read_barrier_depends(); /* see post_one_send() */
 		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
@@ -119,7 +118,6 @@ int hfi1_make_uc_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 		    RVT_PROCESS_NEXT_SEND_OK))
 			goto bail;
 		/* Check if send work queue is empty. */
-		smp_read_barrier_depends(); /* see post_one_send() */
 		if (qp->s_cur == READ_ONCE(qp->s_head)) {
 			clear_ahg(qp);
 			goto bail;

drivers/infiniband/hw/hfi1/ud.c

@@ -486,7 +486,6 @@ int hfi1_make_ud_req(struct rvt_qp *qp, struct hfi1_pkt_state *ps)
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		smp_read_barrier_depends(); /* see post_one_send */
 		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
@@ -500,7 +499,6 @@ 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 == READ_ONCE(qp->s_head))
 		goto bail;
 

drivers/infiniband/hw/qib/qib_rc.c

@@ -246,7 +246,6 @@ int qib_make_rc_req(struct rvt_qp *qp, unsigned long *flags)
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		smp_read_barrier_depends(); /* see post_one_send() */
 		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
@@ -293,7 +292,6 @@ int qib_make_rc_req(struct rvt_qp *qp, unsigned long *flags)
 		newreq = 0;
 		if (qp->s_cur == qp->s_tail) {
 			/* Check if send work queue is empty. */
-			smp_read_barrier_depends(); /* see post_one_send() */
 			if (qp->s_tail == READ_ONCE(qp->s_head))
 				goto bail;
 			/*
@@ -1340,7 +1338,6 @@ static void qib_rc_rcv_resp(struct qib_ibport *ibp,
 		goto ack_done;
 
 	/* Ignore invalid responses. */
-	smp_read_barrier_depends(); /* see post_one_send */
 	if (qib_cmp24(psn, READ_ONCE(qp->s_next_psn)) >= 0)
 		goto ack_done;
 

drivers/infiniband/hw/qib/qib_ruc.c

@@ -367,7 +367,6 @@ static void qib_ruc_loopback(struct rvt_qp *sqp)
 	sqp->s_flags |= RVT_S_BUSY;
 
 again:
-	smp_read_barrier_depends(); /* see post_one_send() */
 	if (sqp->s_last == READ_ONCE(sqp->s_head))
 		goto clr_busy;
 	wqe = rvt_get_swqe_ptr(sqp, sqp->s_last);

drivers/infiniband/hw/qib/qib_uc.c

@@ -60,7 +60,6 @@ int qib_make_uc_req(struct rvt_qp *qp, unsigned long *flags)
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		smp_read_barrier_depends(); /* see post_one_send() */
 		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
@@ -90,7 +89,6 @@ int qib_make_uc_req(struct rvt_qp *qp, unsigned long *flags)
 		    RVT_PROCESS_NEXT_SEND_OK))
 			goto bail;
 		/* Check if send work queue is empty. */
-		smp_read_barrier_depends(); /* see post_one_send() */
 		if (qp->s_cur == READ_ONCE(qp->s_head))
 			goto bail;
 		/*

drivers/infiniband/hw/qib/qib_ud.c

@@ -252,7 +252,6 @@ int qib_make_ud_req(struct rvt_qp *qp, unsigned long *flags)
 		if (!(ib_rvt_state_ops[qp->state] & RVT_FLUSH_SEND))
 			goto bail;
 		/* We are in the error state, flush the work request. */
-		smp_read_barrier_depends(); /* see post_one_send */
 		if (qp->s_last == READ_ONCE(qp->s_head))
 			goto bail;
 		/* If DMAs are in progress, we can't flush immediately. */
@@ -266,7 +265,6 @@ int qib_make_ud_req(struct rvt_qp *qp, unsigned long *flags)
 	}
 
 	/* see post_one_send() */
-	smp_read_barrier_depends();
 	if (qp->s_cur == READ_ONCE(qp->s_head))
 		goto bail;
 

drivers/infiniband/sw/rdmavt/qp.c

@@ -1684,7 +1684,6 @@ static inline int rvt_qp_is_avail(
 	/* non-reserved operations */
 	if (likely(qp->s_avail))
 		return 0;
-	smp_read_barrier_depends(); /* see rc.c */
 	slast = READ_ONCE(qp->s_last);
 	if (qp->s_head >= slast)
 		avail = qp->s_size - (qp->s_head - slast);