* [Question] netfilter, xt_target->target and xt_target->checkentry locks
@ 2010-06-09 12:21 Jiri Pirko
2010-06-09 12:37 ` Jan Engelhardt
0 siblings, 1 reply; 7+ messages in thread
From: Jiri Pirko @ 2010-06-09 12:21 UTC (permalink / raw)
To: kaber; +Cc: netfilter, bart.de.schuymer, davem, shemminger
Hi Patrick.
Once module registers it's struct xt_target by xt_register_target and ->target
and ->checkentry funtions are called later, is there any lock guaranteed to be
held?
From what I see for ->target it looks like rcu_read_lock is held, but I'm not
sure for all paths. There would be nice to put a comment into struct xt_target
definition regarding locks.
Asking because I found several places where dev->br_port is referenced directly
(without rcu_dereference).
Thanks a lot.
Jirka
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Question] netfilter, xt_target->target and xt_target->checkentry locks
2010-06-09 12:21 [Question] netfilter, xt_target->target and xt_target->checkentry locks Jiri Pirko
@ 2010-06-09 12:37 ` Jan Engelhardt
2010-06-09 13:00 ` Jiri Pirko
0 siblings, 1 reply; 7+ messages in thread
From: Jan Engelhardt @ 2010-06-09 12:37 UTC (permalink / raw)
To: Jiri Pirko; +Cc: kaber, netfilter, bart.de.schuymer, davem, shemminger
On Wednesday 2010-06-09 14:21, Jiri Pirko wrote:
>Hi Patrick.
>
>Once module registers it's struct xt_target by xt_register_target and
>->target and ->checkentry funtions are called later, is there any lock
>guaranteed to be held?
From what I see for ->target it looks like rcu_read_lock is held, but
>I'm not sure for all paths. There would be nice to put a comment into
>struct xt_target definition regarding locks.
Though nf_hook_slow invokes rcu_read_lock, that should not be a formal
guarantee that Xtables extensions run with RCU. See xt_TCPMSS for
example.
>Asking because I found several places where dev->br_port is
>referenced directly (without rcu_dereference).
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Question] netfilter, xt_target->target and xt_target->checkentry locks
2010-06-09 12:37 ` Jan Engelhardt
@ 2010-06-09 13:00 ` Jiri Pirko
2010-06-09 13:03 ` Patrick McHardy
0 siblings, 1 reply; 7+ messages in thread
From: Jiri Pirko @ 2010-06-09 13:00 UTC (permalink / raw)
To: Jan Engelhardt; +Cc: kaber, netfilter, bart.de.schuymer, davem, shemminger
Wed, Jun 09, 2010 at 02:37:51PM CEST, jengelh@medozas.de wrote:
>On Wednesday 2010-06-09 14:21, Jiri Pirko wrote:
>
>>Hi Patrick.
>>
>>Once module registers it's struct xt_target by xt_register_target and
>>->target and ->checkentry funtions are called later, is there any lock
>>guaranteed to be held?
>>From what I see for ->target it looks like rcu_read_lock is held, but
>>I'm not sure for all paths. There would be nice to put a comment into
>>struct xt_target definition regarding locks.
>
>Though nf_hook_slow invokes rcu_read_lock, that should not be a formal
>guarantee that Xtables extensions run with RCU. See xt_TCPMSS for
>example.
A was afraid of it. Thanks.
>
>>Asking because I found several places where dev->br_port is
>>referenced directly (without rcu_dereference).
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Question] netfilter, xt_target->target and xt_target->checkentry locks
2010-06-09 13:00 ` Jiri Pirko
@ 2010-06-09 13:03 ` Patrick McHardy
2010-06-09 13:13 ` Jiri Pirko
0 siblings, 1 reply; 7+ messages in thread
From: Patrick McHardy @ 2010-06-09 13:03 UTC (permalink / raw)
To: Jiri Pirko; +Cc: Jan Engelhardt, netfilter, bart.de.schuymer, davem, shemminger
Jiri Pirko wrote:
> Wed, Jun 09, 2010 at 02:37:51PM CEST, jengelh@medozas.de wrote:
>
>> On Wednesday 2010-06-09 14:21, Jiri Pirko wrote:
>>
>>
>>> Hi Patrick.
>>>
>>> Once module registers it's struct xt_target by xt_register_target and
>>> ->target and ->checkentry funtions are called later, is there any lock
>>> guaranteed to be held?
>>>
>> >From what I see for ->target it looks like rcu_read_lock is held, but
>>
>>> I'm not sure for all paths. There would be nice to put a comment into
>>> struct xt_target definition regarding locks.
>>>
>> Though nf_hook_slow invokes rcu_read_lock, that should not be a formal
>> guarantee that Xtables extensions run with RCU. See xt_TCPMSS for
>> example.
>>
>
> A was afraid of it. Thanks.
We actually assume this in all conntrack helpers, so I don't see anything
wrong with making the same assumption in xtables modules, as long as
its documented.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Question] netfilter, xt_target->target and xt_target->checkentry locks
2010-06-09 13:03 ` Patrick McHardy
@ 2010-06-09 13:13 ` Jiri Pirko
2010-06-09 13:26 ` Patrick McHardy
0 siblings, 1 reply; 7+ messages in thread
From: Jiri Pirko @ 2010-06-09 13:13 UTC (permalink / raw)
To: Patrick McHardy
Cc: Jan Engelhardt, netfilter, bart.de.schuymer, davem, shemminger
Wed, Jun 09, 2010 at 03:03:19PM CEST, kaber@trash.net wrote:
>Jiri Pirko wrote:
>> Wed, Jun 09, 2010 at 02:37:51PM CEST, jengelh@medozas.de wrote:
>>
>>> On Wednesday 2010-06-09 14:21, Jiri Pirko wrote:
>>>
>>>
>>>> Hi Patrick.
>>>>
>>>> Once module registers it's struct xt_target by xt_register_target and
>>>> ->target and ->checkentry funtions are called later, is there any lock
>>>> guaranteed to be held?
>>>>
>>> >From what I see for ->target it looks like rcu_read_lock is held, but
>>>
>>>> I'm not sure for all paths. There would be nice to put a comment into
>>>> struct xt_target definition regarding locks.
>>>>
>>> Though nf_hook_slow invokes rcu_read_lock, that should not be a formal
>>> guarantee that Xtables extensions run with RCU. See xt_TCPMSS for
>>> example.
>>>
>>
>> A was afraid of it. Thanks.
>
>We actually assume this in all conntrack helpers, so I don't see anything
>wrong with making the same assumption in xtables modules, as long as
>its documented.
Where this is documented please?
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Question] netfilter, xt_target->target and xt_target->checkentry locks
2010-06-09 13:13 ` Jiri Pirko
@ 2010-06-09 13:26 ` Patrick McHardy
2010-06-09 14:06 ` Jiri Pirko
0 siblings, 1 reply; 7+ messages in thread
From: Patrick McHardy @ 2010-06-09 13:26 UTC (permalink / raw)
To: Jiri Pirko; +Cc: Jan Engelhardt, netfilter, bart.de.schuymer, davem, shemminger
Jiri Pirko wrote:
> Wed, Jun 09, 2010 at 03:03:19PM CEST, kaber@trash.net wrote:
>
>> Jiri Pirko wrote:
>>
>>> Wed, Jun 09, 2010 at 02:37:51PM CEST, jengelh@medozas.de wrote:
>>>
>>>
>>>> On Wednesday 2010-06-09 14:21, Jiri Pirko wrote:
>>>>
>>>>
>>>>
>>>>> Hi Patrick.
>>>>>
>>>>> Once module registers it's struct xt_target by xt_register_target and
>>>>> ->target and ->checkentry funtions are called later, is there any lock
>>>>> guaranteed to be held?
>>>>>
>>>>>
>>>> >From what I see for ->target it looks like rcu_read_lock is held, but
>>>>
>>>>
>>>>> I'm not sure for all paths. There would be nice to put a comment into
>>>>> struct xt_target definition regarding locks.
>>>>>
>>>>>
>>>> Though nf_hook_slow invokes rcu_read_lock, that should not be a formal
>>>> guarantee that Xtables extensions run with RCU. See xt_TCPMSS for
>>>> example.
>>>>
>>>>
>>> A was afraid of it. Thanks.
>>>
>> We actually assume this in all conntrack helpers, so I don't see anything
>> wrong with making the same assumption in xtables modules, as long as
>> its documented.
>>
>
> Where this is documented please?
>
In the spots relying on this ("/* rcu_read_lock()ed by nf_hook_slow */").
Actually its not the helpers, but other parts of conntrack.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [Question] netfilter, xt_target->target and xt_target->checkentry locks
2010-06-09 13:26 ` Patrick McHardy
@ 2010-06-09 14:06 ` Jiri Pirko
0 siblings, 0 replies; 7+ messages in thread
From: Jiri Pirko @ 2010-06-09 14:06 UTC (permalink / raw)
To: Patrick McHardy
Cc: Jan Engelhardt, netfilter, bart.de.schuymer, davem, shemminger
Wed, Jun 09, 2010 at 03:26:44PM CEST, kaber@trash.net wrote:
>Jiri Pirko wrote:
>> Wed, Jun 09, 2010 at 03:03:19PM CEST, kaber@trash.net wrote:
>>
>>> Jiri Pirko wrote:
>>>
>>>> Wed, Jun 09, 2010 at 02:37:51PM CEST, jengelh@medozas.de wrote:
>>>>
>>>>
>>>>> On Wednesday 2010-06-09 14:21, Jiri Pirko wrote:
>>>>>
>>>>>
>>>>>
>>>>>> Hi Patrick.
>>>>>>
>>>>>> Once module registers it's struct xt_target by xt_register_target and
>>>>>> ->target and ->checkentry funtions are called later, is there any lock
>>>>>> guaranteed to be held?
>>>>>>
>>>>>>
>>>>> >From what I see for ->target it looks like rcu_read_lock is held, but
>>>>>
>>>>>
>>>>>> I'm not sure for all paths. There would be nice to put a comment into
>>>>>> struct xt_target definition regarding locks.
>>>>>>
>>>>>>
>>>>> Though nf_hook_slow invokes rcu_read_lock, that should not be a formal
>>>>> guarantee that Xtables extensions run with RCU. See xt_TCPMSS for
>>>>> example.
>>>>>
>>>>>
>>>> A was afraid of it. Thanks.
>>>>
>>> We actually assume this in all conntrack helpers, so I don't see anything
>>> wrong with making the same assumption in xtables modules, as long as
>>> its documented.
>>>
>>
>> Where this is documented please?
>>
>
>In the spots relying on this ("/* rcu_read_lock()ed by nf_hook_slow */").
>Actually its not the helpers, but other parts of conntrack.
Ok, I'll add it to appropriate places. And in xt_TCPMSS, rcu_read_lock can be
removed too.
Thanks.
Jirka
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2010-06-09 14:06 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
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2010-06-09 12:21 [Question] netfilter, xt_target->target and xt_target->checkentry locks Jiri Pirko
2010-06-09 12:37 ` Jan Engelhardt
2010-06-09 13:00 ` Jiri Pirko
2010-06-09 13:03 ` Patrick McHardy
2010-06-09 13:13 ` Jiri Pirko
2010-06-09 13:26 ` Patrick McHardy
2010-06-09 14:06 ` Jiri Pirko
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