On Thu, Mar 27, 2008 at 05:34:18PM -0700, David Miller wrote:

The first cpu will get into __qdisc_run(), but the other
ones will just q->enqueue() and exit since the first cpu
has indicated it is processing the qdisc.

Indeed.  Since I created the problem it's only fair that I get
to fix it too :)

[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.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} [off-list ref]
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
--

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 10b5c08..80d53dd 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c

@@ -187,6 +187,10 @@ void __qdisc_run(struct net_device *dev)
 	do {
 		if (!qdisc_restart(dev))
 			break;
+		if (need_resched()) {
+			netif_schedule(dev);
+			break;
+		}
 	} while (!netif_queue_stopped(dev));
 
 	clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);