netdev - Re: [patch net-next 3/6] net_sched: cls_bpf: remove faulty use of list_for_each_entry

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Message-ID: <20141203152051.GK1860@nanopsycho.orion>
Date:	Wed, 3 Dec 2014 16:20:51 +0100
From:	Jiri Pirko <jiri@...nulli.us>
To:	Jamal Hadi Salim <jhs@...atatu.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [patch net-next 3/6] net_sched: cls_bpf: remove faulty use of
 list_for_each_entry_rcu

Wed, Dec 03, 2014 at 03:37:46PM CET, jhs@...atatu.com wrote:
>On 12/03/14 08:26, Jiri Pirko wrote:
>>Wed, Dec 03, 2014 at 01:51:15PM CET, jhs@...atatu.com wrote:
>
>>>I think this may be problematic. Doesnt a flush operation also use the
>>>walker?
>>
>>I don't believe so. Just look at tc_dump_tfilter.
>>
>
>Actually we cant flush filters (we could actions).
>
>>But even if that would the the case, _rcu variant is wrong (yep, it
>>would have to be replaced by _safe variant then).
>>
>
>Sorry, still humping on the get part:
>that gets invoked for del for a filter that may be in use in the
>datapath. del uses rcu - should get not use rcu in such a case?

Yep, but this is updater, protected by rtnl. _rcu list travelsal variant
should be used by reader only (classify callback in cls case).

get op is only called from tc_ctl_tfilter which is always called with
rtnl held.

>
>cheers,
>jamal
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