Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3)

Jan Engelhardt
2009-04-16T12:24:21Z

On Thursday 2009-04-16 14:12, Patrick McHardy wrote:
> Jan Engelhardt wrote:
>> On Wednesday 2009-04-15 23:07, Eric Dumazet wrote:
>>> Stephen Hemminger a écrit :
>>>> Looks like there is some recursive path into ip_tables that makes the
>>>> per-cpu spinlock break. I get lockup's with KVM networking.
>>>>
>>>> Suggestions?
>>> Well, it seems original patch was not so bad after all
>>>
>>> http://lists.netfilter.org/pipermail/netfilter-devel/2006-January/023175.html
>>>
>>> So change per-cpu spinlocks to per-cpu rwlocks
>>> and use read_lock() in ipt_do_table() to allow recursion...
>>>
>> iptables cannot quite recurse into itself due to the comefrom stuff.
>
> Actually it can by using the REJECT target:

Yes, but it has to return an absolute verdict (which REJECT does),
so it's not really a recursion, it's more like a goto without return.