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authorHerbert Xu <herbert@gondor.apana.org.au>2006-06-19 23:57:59 -0700
committerDavid S. Miller <davem@davemloft.net>2006-06-19 23:57:59 -0700
commit48d83325b61043e3bbd24dd37b9fe433744cf330 (patch)
tree00dc0682be0f096676ac885152b4ae14c4137338 /include
parentd6cc7f1a3b33c89c91b3dfce1ff053178893470e (diff)
[NET]: Prevent multiple qdisc runs
Having two or more qdisc_run's contend against each other is bad because it can induce packet reordering if the packets have to be requeued. It appears that this is an unintended consequence of relinquinshing the queue lock while transmitting. That in turn is needed for devices that spend a lot of time in their transmit routine. There are no advantages to be had as devices with queues are inherently single-threaded (the loopback device is not but then it doesn't have a queue). Even if you were to add a queue to a parallel virtual device (e.g., bolt a tbf filter in front of an ipip tunnel device), you would still want to process the queue in sequence to ensure that the packets are ordered correctly. The solution here is to steal a bit from net_device to prevent this. BTW, as qdisc_restart is no longer used by anyone as a module inside the kernel (IIRC it used to with netif_wake_queue), I have not exported the new __qdisc_run function. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
-rw-r--r--include/linux/netdevice.h1
-rw-r--r--include/net/pkt_sched.h7
2 files changed, 5 insertions, 3 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e432b743dda..39919c882a2 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -233,6 +233,7 @@ enum netdev_state_t
__LINK_STATE_RX_SCHED,
__LINK_STATE_LINKWATCH_PENDING,
__LINK_STATE_DORMANT,
+ __LINK_STATE_QDISC_RUNNING,
};
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index b94d1ad92c4..75b5b9333fc 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -218,12 +218,13 @@ extern struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r,
struct rtattr *tab);
extern void qdisc_put_rtab(struct qdisc_rate_table *tab);
-extern int qdisc_restart(struct net_device *dev);
+extern void __qdisc_run(struct net_device *dev);
static inline void qdisc_run(struct net_device *dev)
{
- while (!netif_queue_stopped(dev) && qdisc_restart(dev) < 0)
- /* NOTHING */;
+ if (!netif_queue_stopped(dev) &&
+ !test_and_set_bit(__LINK_STATE_QDISC_RUNNING, &dev->state))
+ __qdisc_run(dev);
}
extern int tc_classify(struct sk_buff *skb, struct tcf_proto *tp,