This is a note to let you know that I've just added the patch titled
net: ethernet: ti: cpsw: fix net watchdog timeout
to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: net-ethernet-ti-cpsw-fix-net-watchdog-timeout.patch and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Tue Mar 6 19:02:56 PST 2018
From: Grygorii Strashko grygorii.strashko@ti.com Date: Tue, 6 Feb 2018 19:17:06 -0600 Subject: net: ethernet: ti: cpsw: fix net watchdog timeout
From: Grygorii Strashko grygorii.strashko@ti.com
[ 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 --- drivers/net/ethernet/ti/cpsw.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
--- 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(s 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(s * 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; }
Patches currently in stable-queue which might be from grygorii.strashko@ti.com are
queue-4.15/net-ethernet-ti-cpsw-fix-net-watchdog-timeout.patch