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bridge: don't allow setting hello time to zero

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Dushan Tcholich reports that on his system ksoftirqd can consume
between %6 to %10 of cpu time, and cause ~200 context switches per
second.

He then correlated this with a report by bdupree@techfinesse.com:

	http://marc.info/?l=linux-kernel&m=119613299024398&w=2

and the culprit cause seems to be starting the bridge interface.
In particular, when starting the bridge interface, his scripts
are specifying a hello timer interval of "0".

The bridge hello time can't be safely set to values less than 1
second, otherwise it is possible to end up with a runaway timer.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger
2008-09-08 13:44:40 -07:00
committed by David S. Miller
parent d315492b1a
commit 8d4698f7a5
2 changed files with 25 additions and 9 deletions
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8
net/bridge/br_ioctl.c
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@ -188,15 +188,21 @@ static int old_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
return 0;
case BRCTL_SET_BRIDGE_HELLO_TIME:
{
unsigned long t = clock_t_to_jiffies(args[1]);
if (!capable(CAP_NET_ADMIN))
return -EPERM;
if (t < HZ)
return -EINVAL;
spin_lock_bh(&br->lock);
br->bridge_hello_time = clock_t_to_jiffies(args[1]);
br->bridge_hello_time = t;
if (br_is_root_bridge(br))
br->hello_time = br->bridge_hello_time;
spin_unlock_bh(&br->lock);
return 0;
}
case BRCTL_SET_BRIDGE_MAX_AGE:
if (!capable(CAP_NET_ADMIN))