netdev - Re: [PATCH] net: sched: cls_cgroup tear down exts and ematch from rcu callback

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Message-Id: <20141005.213146.1400362219156302379.davem@davemloft.net>
Date:	Sun, 05 Oct 2014 21:31:46 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	john.fastabend@...il.com
Cc:	xiyou.wangcong@...il.com, netdev@...r.kernel.org, jhs@...atatu.com,
	eric.dumazet@...il.com
Subject: Re: [PATCH] net: sched: cls_cgroup tear down exts and ematch from
 rcu callback

From: John Fastabend <john.fastabend@...il.com>
Date: Fri, 03 Oct 2014 09:33:35 -0700

> It is not RCU safe to destroy the action chain while there
> is a possibility of readers accessing it. Move this code
> into the rcu callback using the same rcu callback used in the
> code patch to make a change to head.
> 
> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
 ...
> @@ -156,10 +156,8 @@ static void cls_cgroup_destroy(struct tcf_proto *tp)
>  	struct cls_cgroup_head *head = rtnl_dereference(tp->root);
>  
>  	if (head) {
> -		tcf_exts_destroy(&head->exts);
> -		tcf_em_tree_destroy(head->net, &head->ematches);
>  		RCU_INIT_POINTER(tp->root, NULL);
> -		kfree_rcu(head, rcu);
> +		call_rcu(&head->rcu, cls_cgroup_destroy_rcu);
>  	}

tcf_em_tree_destroy() takes head->tp as it's first argument in my
net-next tree, maybe you need to respin this?
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