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@xxxxxxxxx>
Tested-by: Ulrich Weber <uw@xxxxxxxxx>
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>
---
I had a look at converting the ipv6 notifier to a blocking one
but I found this too difficult (RTNL held? How to defer notifier calls
from packet path)? Just doing it for masquerade is a lot simpler:
- we only care about NETDEV_DOWN, so no extra work needed in most cases
- can just ignore the notification if too much work is already queued
net/ipv6/netfilter/nf_nat_masquerade_ipv6.c | 74 +++++++++++++++++++++++++++--
net/netfilter/nf_conntrack_core.c | 5 ++
2 files changed, 76 insertions(+), 3 deletions(-)
diff --git a/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c b/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c
index 31ba7ca..3878ac2 100644
--- a/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c
+++ b/net/ipv6/netfilter/nf_nat_masquerade_ipv6.c
@@ -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;
+
+ 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;
- netdev_notifier_info_init(&info, ifa->idev->dev);
- return masq_device_event(this, event, &info);
+ 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 = {
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 3cb3cb8..25f1696 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1394,6 +1394,7 @@ 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) {
@@ -1406,6 +1407,7 @@ 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:
@@ -1422,6 +1424,8 @@ 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))
@@ -1430,6 +1434,7 @@ 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);
--
2.4.10
--
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