From 2ba2506ca7ca62c56edaa334b0fe61eb5eab6ab0 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Fri, 28 Mar 2008 16:25:26 -0700
Subject: [PATCH] [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>
---
net/sched/sch_generic.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 10b5c0887fff..b741618e4d54 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -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;
+
+ /*
+ * 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;
- } while (!netif_queue_stopped(dev));
+ }
+ }
clear_bit(__LINK_STATE_QDISC_RUNNING, &dev->state);
}
--
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