[PATCH] drm/msm: use proper memory barriers for updating tail/head

[Rob Clark <robdclark@gmail.com>]

Fixes intermittent corruption of cmdstream dump.

Signed-off-by: Rob Clark <robdclark@gmail.com>
---
 drivers/gpu/drm/msm/msm_rd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_rd.c b/drivers/gpu/drm/msm/msm_rd.c
index 5c087a4228ff..918c65e19964 100644
--- a/drivers/gpu/drm/msm/msm_rd.c
+++ b/drivers/gpu/drm/msm/msm_rd.c
@@ -120,7 +120,7 @@ static void rd_write(struct msm_rd_state *rd, const void *buf, int sz)
 		n = min(sz, circ_space_to_end(&rd->fifo));
 		memcpy(fptr, ptr, n);
 
-		fifo->head = (fifo->head + n) & (BUF_SZ - 1);
+		smp_store_release(&fifo->head, (fifo->head + n) & (BUF_SZ - 1));
 		sz  -= n;
 		ptr += n;
 
@@ -157,7 +157,7 @@ static ssize_t rd_read(struct file *file, char __user *buf,
 		goto out;
 	}
 
-	fifo->tail = (fifo->tail + n) & (BUF_SZ - 1);
+	smp_store_release(&fifo->tail, (fifo->tail + n) & (BUF_SZ - 1));
 	*ppos += n;
 
 	wake_up_all(&rd->fifo_event);
-- 
2.13.5