Changli Gao wrote:
> On Thu, Apr 15, 2010 at 11:35 PM, Patrick McHardy <kaber@xxxxxxxxx> wrote:
>> Changli Gao wrote:
>>> static int
>>> nfqnl_rcv_nl_event(struct notifier_block *this,
>>> unsigned long event, void *ptr)
>>> {
>>> struct netlink_notify *n = ptr;
>>>
>>> if (event == NETLINK_URELEASE && n->protocol == NETLINK_NETFILTER) {
>>> int i;
>>>
>>> /* destroy all instances for this pid */
>>> spin_lock(&instances_lock);
>>> for (i = 0; i < INSTANCE_BUCKETS; i++) {
>>> struct hlist_node *tmp, *t2;
>>> struct nfqnl_instance *inst;
>>> struct hlist_head *head = &instance_table[i];
>>>
>>> hlist_for_each_entry_safe(inst, tmp, t2, head, hlist) {
>>> if ((n->net == &init_net) &&
>>> (n->pid == inst->peer_pid))
>>> __instance_destroy(inst);
>>> }
>>> }
>>> spin_unlock(&instances_lock);
>>> }
>>> return NOTIFY_DONE;
>>> }
>>>
>>> static struct notifier_block nfqnl_rtnl_notifier = {
>>> .notifier_call = nfqnl_rcv_nl_event,
>>> };
>>>
>> Ah, right. So call nfnl_lock() or convert the spinlock to a
>> mutex.
>>
>
> We can't convert the spinlock to a mutex simply. The notifier chain is
> an atomic notifier chain.
Well, then use reference counting, redo the lookup, or whatever.
Really, this isn't that hard.
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