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authorDavid S. Miller <davem@davemloft.net>2008-01-04 23:54:06 -0800
committerDavid S. Miller <davem@davemloft.net>2008-01-08 23:29:56 -0800
commit3ebebccf89b1b6e4fec4de05b245d6c459f27ce8 (patch)
tree2f69bd73412f9a986c739e87326ebcc5cf4e68af
parent792dd90f114a48c210c566f3642b26f699702cb7 (diff)
[NIU]: Fix potentially stuck TCP socket send queues.
It is possible for the TX ring to have packets sit in it for unbounded amounts of time. The only way to defer TX interrupts in the chip is to periodically set "mark" bits, when processing of a TX descriptor with the mark bit set is complete it triggers the interrupt for the TX queue's LDG. A consequence of this kind of scheme is that if packet flow suddenly stops, the remaining TX packets will just sit there. If this happens, since those packets could be charged to TCP socket send queues, such sockets could get stuck. The simplest solution is to divorce the socket ownership of the packet once the device takes the SKB, by using skb_orphan() in niu_start_xmit(). In hindsight, it would have been much nicer if the chip provided two interrupt sources for TX (like basically every other ethernet chip does). Namely, keep the "mark" bit, but also signal the LDG when the TX queue becomes completely empty. That way there is no need to have a deadlock breaker like this. Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/niu.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/net/niu.c b/drivers/net/niu.c
index babb1ef37e3..ac361642567 100644
--- a/drivers/net/niu.c
+++ b/drivers/net/niu.c
@@ -5208,7 +5208,8 @@ static int niu_start_xmit(struct sk_buff *skb, struct net_device *dev)
}
kfree_skb(skb);
skb = skb_new;
- }
+ } else
+ skb_orphan(skb);
align = ((unsigned long) skb->data & (16 - 1));
headroom = align + sizeof(struct tx_pkt_hdr);