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netfilter: conntrack: resched in nf_ct_iterate_cleanup 

Ulrich reports soft lockup with following (shortened) callchain:

NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s!
__netif_receive_skb_core+0x6e4/0x774
process_backlog+0x94/0x160
net_rx_action+0x88/0x178
call_do_softirq+0x24/0x3c
do_softirq+0x54/0x6c
__local_bh_enable_ip+0x7c/0xbc
nf_ct_iterate_cleanup+0x11c/0x22c [nf_conntrack]
masq_inet_event+0x20/0x30 [nf_nat_masquerade_ipv6]
atomic_notifier_call_chain+0x1c/0x2c
ipv6_del_addr+0x1bc/0x220 [ipv6]

Problem is that nf_ct_iterate_cleanup can run for a very long time
since it can be interrupted by softirq processing.
Moreover, atomic_notifier_call_chain runs with rcu readlock held.

So lets call cond_resched() in nf_ct_iterate_cleanup and defer
the call to a work queue for the atomic_notifier_call_chain case.

We also need another cond_resched in get_next_corpse, since we
have to deal with iter() always returning false, in that case
get_next_corpse will walk entire conntrack table.

Reported-by: Ulrich Weber <uw@ocedo.com>
Tested-by: Ulrich Weber <uw@ocedo.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2016-01-20 11:16:43 +01:00 committed by Pablo Neira Ayuso
parent 53729eb174
commit d93c6258ee
2 changed files with 76 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

74
net/ipv6/netfilter/nf_nat_masquerade_ipv6.c
View File

@ -21,6 +21,10 @@
#include <net/ipv6.h>
#include <net/netfilter/ipv6/nf_nat_masquerade.h>
#define MAX_WORK_COUNT 16
static atomic_t v6_worker_count;
unsigned int
nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range *range,
const struct net_device *out)
@ -78,14 +82,78 @@ static struct notifier_block masq_dev_notifier = {
.notifier_call = masq_device_event,
};
struct masq_dev_work {
struct work_struct work;
struct net *net;
int ifindex;
};
static void iterate_cleanup_work(struct work_struct *work)
{
struct masq_dev_work *w;
long index;
w = container_of(work, struct masq_dev_work, work);
index = w->ifindex;
nf_ct_iterate_cleanup(w->net, device_cmp, (void *)index, 0, 0);
put_net(w->net);
kfree(w);
atomic_dec(&v6_worker_count);
module_put(THIS_MODULE);
}
/* ipv6 inet notifier is an atomic notifier, i.e. we cannot
* schedule.
*
* Unfortunately, nf_ct_iterate_cleanup can run for a long
* time if there are lots of conntracks and the system
* handles high softirq load, so it frequently calls cond_resched
* while iterating the conntrack table.
*
* So we defer nf_ct_iterate_cleanup walk to the system workqueue.
*
* As we can have 'a lot' of inet_events (depending on amount
* of ipv6 addresses being deleted), we also need to add an upper
* limit to the number of queued work items.
*/
static int masq_inet_event(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct inet6_ifaddr *ifa = ptr;
struct netdev_notifier_info info;
const struct net_device *dev;
struct masq_dev_work *w;
struct net *net;
netdev_notifier_info_init(&info, ifa->idev->dev);
return masq_device_event(this, event, &info);
if (event != NETDEV_DOWN ||
atomic_read(&v6_worker_count) >= MAX_WORK_COUNT)
return NOTIFY_DONE;
dev = ifa->idev->dev;
net = maybe_get_net(dev_net(dev));
if (!net)
return NOTIFY_DONE;
if (!try_module_get(THIS_MODULE))
goto err_module;
w = kmalloc(sizeof(*w), GFP_ATOMIC);
if (w) {
atomic_inc(&v6_worker_count);
INIT_WORK(&w->work, iterate_cleanup_work);
w->ifindex = dev->ifindex;
w->net = net;
schedule_work(&w->work);
return NOTIFY_DONE;
}
module_put(THIS_MODULE);
err_module:
put_net(net);
return NOTIFY_DONE;
}
static struct notifier_block masq_inet_notifier = {

5
net/netfilter/nf_conntrack_core.c
View File

@ -1412,6 +1412,7 @@ get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data),
}
spin_unlock(lockp);
local_bh_enable();
cond_resched();
}
for_each_possible_cpu(cpu) {
@ -1424,6 +1425,7 @@ get_next_corpse(struct net *net, int (*iter)(struct nf_conn *i, void *data),
set_bit(IPS_DYING_BIT, &ct->status);
}
spin_unlock_bh(&pcpu->lock);
cond_resched();
}
return NULL;
found:
@ -1440,6 +1442,8 @@ void nf_ct_iterate_cleanup(struct net *net,
struct nf_conn *ct;
unsigned int bucket = 0;
might_sleep();
while ((ct = get_next_corpse(net, iter, data, &bucket)) != NULL) {
/* Time to push up daises... */
if (del_timer(&ct->timeout))
@ -1448,6 +1452,7 @@ void nf_ct_iterate_cleanup(struct net *net,
/* ... else the timer will get him soon. */
nf_ct_put(ct);
cond_resched();
}
}
EXPORT_SYMBOL_GPL(nf_ct_iterate_cleanup);