netdev - Re: net: rcu warnings in ip6fl_get

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Message-ID: <CA+1xoqeND5452=W0HLYoBzfou+0NM_x2d5GubivQX8mKOFExsg@mail.gmail.com>
Date:	Thu, 7 Feb 2013 22:54:48 -0500
From:	Sasha Levin <levinsasha928@...il.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	davem <davem@...emloft.net>, yoshfuji@...ux-ipv6.org
Subject: Re: net: rcu warnings in ip6fl_get_first

On Thu, Feb 7, 2013 at 8:38 PM, Cong Wang <xiyou.wangcong@...il.com> wrote:
> On Thu, 07 Feb 2013 at 19:32 GMT, Sasha Levin <sasha.levin@...cle.com> wrote:
>> Hi guys,
>>
>> I got the following while fuzzing with trinity inside a KVM tools guest:
>>
>> [   51.680236] ===============================
>> [   51.681914] [ INFO: suspicious RCU usage. ]
>> [   51.683610] 3.8.0-rc6-next-20130206-sasha-00028-g83214f7-dirty #276 Tainted: G        W
>> [   51.686703] -------------------------------
>> [   51.688281] net/ipv6/ip6_flowlabel.c:671 suspicious rcu_dereference_check() usage!
>> [   51.691345]
>
> It should use rcu_dereference_bh()...
>
> diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
> index ea42bf4..c50080f 100644
> --- a/net/ipv6/ip6_flowlabel.c
> +++ b/net/ipv6/ip6_flowlabel.c
> @@ -65,13 +65,13 @@ static DEFINE_SPINLOCK(ip6_fl_lock);
>  static DEFINE_SPINLOCK(ip6_sk_fl_lock);
>
>  #define for_each_fl_rcu(hash, fl)                              \
> -       for (fl = rcu_dereference(fl_ht[(hash)]);               \
> +       for (fl = rcu_dereference_bh(fl_ht[(hash)]);            \
>              fl != NULL;                                        \
> -            fl = rcu_dereference(fl->next))
> +            fl = rcu_dereference_hb(fl->next))
>  #define for_each_fl_continue_rcu(fl)                           \
> -       for (fl = rcu_dereference(fl->next);                    \
> +       for (fl = rcu_dereference_bh(fl->next);                 \
>              fl != NULL;                                        \
> -            fl = rcu_dereference(fl->next))
> +            fl = rcu_dereference_bh(fl->next))
>
>  #define for_each_sk_fl_rcu(np, sfl)                            \
>         for (sfl = rcu_dereference_bh(np->ipv6_fl_list);        \

Yup, that's how I fixed it locally and it was running without warnings
for couple of hours now.


Thanks,
Sasha
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