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authorAndreas Herrmann <andreas.herrmann@calxeda.com>2013-11-07 12:07:56 +0100
committerDavid S. Miller <davem@davemloft.net>2013-11-07 19:25:53 -0500
commitb5ad795e52dae6e9f88b193a5e779b70005d005c (patch)
tree520907ecada6e8f2d3ed49e08d7483b98a6115eb
parente21dd863acec8d3bc5166fb2a0c680a9982b37db (diff)
net: calxedaxgmac: Fix panic caused by MTU change of active interface
Changing MTU size of an xgmac network interface while it is active can cause a panic like skbuff: skb_over_panic: text:c03bc62c len:1090 put:1090 head:edfb6900 data:edfb6942 tail:0xedfb6d84 end:0xedfb6bc0 dev:eth0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:126! Internal error: Oops - BUG: 0 [#1] SMP ARM Modules linked in: CPU: 0 PID: 762 Comm: python Tainted: G W 3.10.0-00015-g3e33cd7 #309 task: edcfe000 ti: ed67e000 task.ti: ed67e000 PC is at skb_panic+0x64/0x70 LR is at wake_up_klogd+0x5c/0x68 This happens because xgmac_change_mtu modifies dev->mtu before the network interface is quiesced. And thus there still might be buffers in use which have a buffer size based on the old MTU. To fix this I moved the change of dev->mtu after the call to xgmac_stop. Another modification is required (in xgmac_stop) to ensure that xgmac_xmit is really not called anymore (xgmac_tx_complete might wake up the queue again). I've tested the fix by switching MTU size every second between 600 and 1500 while network traffic was going on. The test box survived a test of several hours (until I've stopped it) whereas w/o this fix above panic occurs after several minutes (at most). Change since v1: - remove call to netif_stop_queue at beginning of xgmac_stop - use netif_tx_disable instead of locking+netif_stop_queue Signed-off-by: Andreas Herrmann <andreas.herrmann@calxeda.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/ethernet/calxeda/xgmac.c10
1 files changed, 4 insertions, 6 deletions
diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index 48f52882a22b..4fc5c8ef5121 100644
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -1060,13 +1060,13 @@ static int xgmac_stop(struct net_device *dev)
{
struct xgmac_priv *priv = netdev_priv(dev);
- netif_stop_queue(dev);
-
if (readl(priv->base + XGMAC_DMA_INTR_ENA))
napi_disable(&priv->napi);
writel(0, priv->base + XGMAC_DMA_INTR_ENA);
+ netif_tx_disable(dev);
+
/* Disable the MAC core */
xgmac_mac_disable(priv->base);
@@ -1370,11 +1370,8 @@ static int xgmac_change_mtu(struct net_device *dev, int new_mtu)
}
old_mtu = dev->mtu;
- dev->mtu = new_mtu;
/* return early if the buffer sizes will not change */
- if (old_mtu <= ETH_DATA_LEN && new_mtu <= ETH_DATA_LEN)
- return 0;
if (old_mtu == new_mtu)
return 0;
@@ -1382,8 +1379,9 @@ static int xgmac_change_mtu(struct net_device *dev, int new_mtu)
if (!netif_running(dev))
return 0;
- /* Bring the interface down and then back up */
+ /* Bring interface down, change mtu and bring interface back up */
xgmac_stop(dev);
+ dev->mtu = new_mtu;
return xgmac_open(dev);
}