linux-kernel - [PATCH v2 2/9] drivers: dma: Replace smp_read_barrier_depends() with lockless

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Date:	Fri, 21 Nov 2014 10:05:56 -0500
From:	Pranith Kumar <bobby.prani@...il.com>
To:	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"David S. Miller" <davem@...emloft.net>,
	Manuel Schölling <manuel.schoelling@....de>,
	Josh Triplett <josh@...htriplett.org>,
	Rashika <rashika.kheria@...il.com>,
	dmaengine@...r.kernel.org (open list:DMA GENERIC OFFLO...),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 2/9] drivers: dma: Replace smp_read_barrier_depends() with lockless_dereference()

Recently lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends(). The following PATCH makes the change.

Signed-off-by: Pranith Kumar <bobby.prani@...il.com>
---
 drivers/dma/ioat/dma_v2.c | 3 +--
 drivers/dma/ioat/dma_v3.c | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index 695483e..0f94d72 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -142,10 +142,9 @@ static void __cleanup(struct ioat2_dma_chan *ioat, dma_addr_t phys_complete)
 
 	active = ioat2_ring_active(ioat);
 	for (i = 0; i < active && !seen_current; i++) {
-		smp_read_barrier_depends();
 		prefetch(ioat2_get_ring_ent(ioat, idx + i + 1));
 		desc = ioat2_get_ring_ent(ioat, idx + i);
-		tx = &desc->txd;
+		tx = &lockless_dereference(desc)->txd;
 		dump_desc_dbg(ioat, desc);
 		if (tx->cookie) {
 			dma_descriptor_unmap(tx);
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index 895f869..cbd0537 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -389,7 +389,6 @@ static void __cleanup(struct ioat2_dma_chan *ioat, dma_addr_t phys_complete)
 	for (i = 0; i < active && !seen_current; i++) {
 		struct dma_async_tx_descriptor *tx;
 
-		smp_read_barrier_depends();
 		prefetch(ioat2_get_ring_ent(ioat, idx + i + 1));
 		desc = ioat2_get_ring_ent(ioat, idx + i);
 		dump_desc_dbg(ioat, desc);
@@ -398,7 +397,7 @@ static void __cleanup(struct ioat2_dma_chan *ioat, dma_addr_t phys_complete)
 		if (device->cap & IOAT_CAP_DWBES)
 			desc_get_errstat(ioat, desc);
 
-		tx = &desc->txd;
+		tx = &lockless_dereference(desc)->txd;
 		if (tx->cookie) {
 			dma_cookie_complete(tx);
 			dma_descriptor_unmap(tx);
-- 
1.9.1

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