netdev - [RESEND net 1/3] net/mlx5: Fix read from coherent memory

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Message-Id: <20180918034928.28651-2-saeedm@mellanox.com>
Date:   Mon, 17 Sep 2018 20:49:26 -0700
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Eli Cohen <eli@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: [RESEND net 1/3] net/mlx5: Fix read from coherent memory

From: Eli Cohen <eli@...lanox.com>

Use accessor function READ_ONCE to read from coherent memory modified
by the device and read by the driver. This becomes most important in
preemptive kernels where cond_resched implementation does not have the
side effect which guaranteed the updated value.

Fixes: 269d26f47f6f ("net/mlx5: Reduce command polling interval")
Signed-off-by: Eli Cohen <eli@...lanox.com>
Reported-by: Jesper Dangaard Brouer <brouer@...hat.com>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/cmd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
index 3ce14d42ddc8..a53736c26c0c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
@@ -206,7 +206,7 @@ static void poll_timeout(struct mlx5_cmd_work_ent *ent)
 	u8 own;
 
 	do {
-		own = ent->lay->status_own;
+		own = READ_ONCE(ent->lay->status_own);
 		if (!(own & CMD_OWNER_HW)) {
 			ent->ret = 0;
 			return;
-- 
2.17.1