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[NET]: Add preemption point in qdisc_run 

The qdisc_run loop is currently unbounded and runs entirely in a
softirq.  This is bad as it may create an unbounded softirq run.

This patch fixes this by calling need_resched and breaking out if
necessary.

It also adds a break out if the jiffies value changes since that would
indicate we've been transmitting for too long which starves other
softirqs.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2008-03-28 16:25:26 -07:00 committed by David S. Miller
parent 32aced7509
commit 2ba2506ca7
1 changed files with 15 additions and 3 deletions
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18
net/sched/sch_generic.c
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@ -184,10 +184,22 @@ static inline int qdisc_restart(struct net_device *dev)
void __qdisc_run(struct net_device *dev)
{
do {
if (!qdisc_restart(dev))
unsigned long start_time = jiffies;
while (qdisc_restart(dev)) {
if (netif_queue_stopped(dev))
break;
} while (!netif_queue_stopped(dev));
/*
* Postpone processing if
* 1. another process needs the CPU;
* 2. we've been doing it for too long.
*/
if (need_resched() || jiffies != start_time) {
netif_schedule(dev);
break;
}
}
clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
}