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

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Date:	Sun, 05 Oct 2014 18:48:20 -0700
From:	John Fastabend <john.fastabend@...il.com>
To:	David Miller <davem@...emloft.net>
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

On 10/05/2014 06:31 PM, David Miller wrote:
> 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?
>

Yep, I'll respin this now sorry about that got a bit out of sync.

Thanks!

-- 
John Fastabend         Intel Corporation
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