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author | Grygorii Strashko <grygorii.strashko@ti.com> | 2018-02-07 04:17:06 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-09 09:41:08 +0300 |
commit | da260080c2e3a80c4b3c70ec6846011137373f2d (patch) | |
tree | b17f6b3fcc526a2c67d94ceb9acff3cf16c5d851 /drivers/net/ethernet/ti | |
parent | 94870df33c9bf52a9be3ed750670520aad43a44e (diff) | |
download | linux-da260080c2e3a80c4b3c70ec6846011137373f2d.tar.xz |
net: ethernet: ti: cpsw: fix net watchdog timeout
[ Upstream commit 62f94c2101f35cd45775df00ba09bde77580e26a ]
It was discovered that simple program which indefinitely sends 200b UDP
packets and runs on TI AM574x SoC (SMP) under RT Kernel triggers network
watchdog timeout in TI CPSW driver (<6 hours run). The network watchdog
timeout is triggered due to race between cpsw_ndo_start_xmit() and
cpsw_tx_handler() [NAPI]
cpsw_ndo_start_xmit()
if (unlikely(!cpdma_check_free_tx_desc(txch))) {
txq = netdev_get_tx_queue(ndev, q_idx);
netif_tx_stop_queue(txq);
^^ as per [1] barier has to be used after set_bit() otherwise new value
might not be visible to other cpus
}
cpsw_tx_handler()
if (unlikely(netif_tx_queue_stopped(txq)))
netif_tx_wake_queue(txq);
and when it happens ndev TX queue became disabled forever while driver's HW
TX queue is empty.
Fix this, by adding smp_mb__after_atomic() after netif_tx_stop_queue()
calls and double check for free TX descriptors after stopping ndev TX queue
- if there are free TX descriptors wake up ndev TX queue.
[1] https://www.kernel.org/doc/html/latest/core-api/atomic_ops.html
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Reviewed-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/net/ethernet/ti')
-rw-r--r-- | drivers/net/ethernet/ti/cpsw.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c index db8a4bcfc6c7..14b646b3b084 100644 --- a/drivers/net/ethernet/ti/cpsw.c +++ b/drivers/net/ethernet/ti/cpsw.c @@ -1618,6 +1618,7 @@ static netdev_tx_t cpsw_ndo_start_xmit(struct sk_buff *skb, q_idx = q_idx % cpsw->tx_ch_num; txch = cpsw->txv[q_idx].ch; + txq = netdev_get_tx_queue(ndev, q_idx); ret = cpsw_tx_packet_submit(priv, skb, txch); if (unlikely(ret != 0)) { cpsw_err(priv, tx_err, "desc submit failed\n"); @@ -1628,15 +1629,26 @@ static netdev_tx_t cpsw_ndo_start_xmit(struct sk_buff *skb, * tell the kernel to stop sending us tx frames. */ if (unlikely(!cpdma_check_free_tx_desc(txch))) { - txq = netdev_get_tx_queue(ndev, q_idx); netif_tx_stop_queue(txq); + + /* Barrier, so that stop_queue visible to other cpus */ + smp_mb__after_atomic(); + + if (cpdma_check_free_tx_desc(txch)) + netif_tx_wake_queue(txq); } return NETDEV_TX_OK; fail: ndev->stats.tx_dropped++; - txq = netdev_get_tx_queue(ndev, skb_get_queue_mapping(skb)); netif_tx_stop_queue(txq); + + /* Barrier, so that stop_queue visible to other cpus */ + smp_mb__after_atomic(); + + if (cpdma_check_free_tx_desc(txch)) + netif_tx_wake_queue(txq); + return NETDEV_TX_BUSY; } |