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From: Yoshihiro Shimoda <>
	Yoshihiro Shimoda <>
Subject: [PATCH] net: renesas: sh_eth: Fix freeing wrong tx descriptor
Date: Tue,  7 Sep 2021 20:29:40 +0900	[thread overview]
Message-ID: <> (raw)

The cur_tx counter must be incremented after TACT bit of
txdesc->status was set. However, a CPU is possible to reorder
instructions and/or memory accesses between cur_tx and
txdesc->status. And then, if TX interrupt happened at such a
timing, the sh_eth_tx_free() may free the descriptor wrongly.
So, add wmb() before cur_tx++.
Otherwise NETDEV WATCHDOG timeout is possible to happen.

Fixes: 86a74ff21a7a ("net: sh_eth: add support for Renesas SuperH Ethernet")
Signed-off-by: Yoshihiro Shimoda <>
 drivers/net/ethernet/renesas/sh_eth.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
index 6c8ba916d1a6..1374faa229a2 100644
--- a/drivers/net/ethernet/renesas/sh_eth.c
+++ b/drivers/net/ethernet/renesas/sh_eth.c
@@ -2533,6 +2533,7 @@ static netdev_tx_t sh_eth_start_xmit(struct sk_buff *skb,
 		txdesc->status |= cpu_to_le32(TD_TACT);
+	wmb(); /* cur_tx must be incremented after TACT bit was set */
 	if (!(sh_eth_read(ndev, EDTRR) & mdp->cd->edtrr_trns))

             reply	other threads:[~2021-09-07 11:30 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-07 11:29 Yoshihiro Shimoda [this message]
2021-09-07 13:10 ` patchwork-bot+netdevbpf
2021-09-07 19:29 ` Sergey Shtylyov
2021-09-08  5:45   ` Yoshihiro Shimoda
2021-09-08  9:46     ` Sergey Shtylyov
2021-09-08 11:43       ` Yoshihiro Shimoda

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