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: <547F9981.8050809@redhat.com>
Date:	Thu, 04 Dec 2014 00:15:13 +0100
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Jamal Hadi Salim <jhs@...atatu.com>
CC:	Jiri Pirko <jiri@...nulli.us>, 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

On 12/03/2014 10:15 PM, Jamal Hadi Salim wrote:
...
> I am not an rcu officionado. So if the control path is doing a non-rcu
> get + rcu-del/change (update) then as long as the fastpath is (read)
> rcu locking we are fine  and nothing will actually happen until the
> fastpath releases and rcu grace period ends, correct?

So if the control path does a list_del_rcu() and call_rcu() under
lock and iterates over list_for_each_entry{,safe}() [which we do
in cls_bpf_delete()], while the fast path [cls_bpf_classify()] uses
a rcu_read_{un,}lock() with *_rcu list iterator, that's fine then,
as it's still guaranteed to be deleted after the grace period. So
Jiri's change looks good to me.

Acked-by: Daniel Borkmann <dborkman@...hat.com>
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