From: Jamal Hadi Salim <jhs@mojatatu•com>
To: John Fastabend <john.fastabend@gmail•com>
Cc: John Fastabend <john.r.fastabend@intel•com>,
Stephen Hemminger <stephen@networkplumber•org>,
Eric Dumazet <eric.dumazet@gmail•com>,
Tom Herbert <therbert@google•com>,
netdev <netdev@vger•kernel.org>
Subject: Re: locating the 'tc actions' hook
Date: Sat, 03 Aug 2013 07:49:45 -0400 [thread overview]
Message-ID: <51FCEE59.1030402@mojatatu.com> (raw)
In-Reply-To: <51FBFE7B.1010602@gmail.com>
On 13-08-02 02:46 PM, John Fastabend wrote:
> Perhaps another incorrect observation but what protects the tc_actions?
>
> Create a series of actions via 'tc actions' which populates the hash
> table protected by hinfo->lock and also rtnetlink is holding the rtnl
> lock.
>
> Add a filter with index hook to get this action graph attached to a
> filters tcf_exts pointer.
>
> Now for what I think is the race, the classifier will call tcf_exts_exec
> which will call tcf_action_exec() and start walking the actions and
> executing them with the qdisc_lock held.
>
> At the same time tcf_action_destroy() may be called via 'tc actions
> delete' which will only hold the rtnl lock via rtnetlink.
>
One runs in user context and the other in softirq context; so it will
work fine.
cheers,
jamal
next prev parent reply other threads:[~2013-08-03 11:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-31 21:19 locating the 'tc actions' hook John Fastabend
2013-08-01 11:40 ` Jamal Hadi Salim
2013-08-01 23:18 ` John Fastabend
2013-08-02 18:46 ` John Fastabend
2013-08-03 11:49 ` Jamal Hadi Salim [this message]
2013-08-03 11:47 ` Jamal Hadi Salim
2013-08-05 16:11 ` John Fastabend
2013-08-12 0:55 ` Jamal Hadi Salim
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