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Message-ID: <502DA666.3020703@windriver.com>
Date: Fri, 17 Aug 2012 10:03:18 +0800
From: Fan Du <fan.du@...driver.com>
To: Paul Gortmaker <paul.gortmaker@...driver.com>
CC: David Miller <davem@...emloft.net>,
Fengguang Wu <fengguang.wu@...el.com>,
Priyanka Jain <Priyanka.Jain@...escale.com>,
<netdev@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: suspicious RCU usage in xfrm_net_init()
On 2012年08月17日 09:34, Paul Gortmaker wrote:
> On Thu, Aug 16, 2012 at 9:07 PM, Fan Du<fan.du@...driver.com> wrote:
>>
>>
>> On 2012年08月16日 23:19, Fengguang Wu wrote:
>>>
>>> Hi Fan,
>>>
>>> On Thu, Aug 16, 2012 at 05:36:35PM +0800, Fan Du wrote:
>>>>
>>>>
>>>> Hi, Fengguang
>>>>
>>>> Could you please try the below patch, see if spewing still there?
>>>> thanks
>>>
>>>
>>> Yes, it worked, thank you very much!
>>>
>>
>> Hi, Dave
>>
>> Could you please pick up this patch?
>
> Please do not make extra work for maintainers by sending attachments,
> or requests for status/merge etc. Your 1st patch had to be manually
> set to an RFC, and now you add another patch less than 24h later.
>
> Please see:
>
> http://patchwork.ozlabs.org/patch/177934/
> http://patchwork.ozlabs.org/patch/178132/
>
> Also, a patch should describe the problem it solves (i.e. the symptom
> the end user sees), and how the problem originated, and why the fix
> in the patch is the _right_ fix. The worst description a commit log
> can have is one that just describes the C change in words, since
> most people can read C on their own.
>
> Here you add "_bh" in the code and then repeat exactly that in
> the commit log. Your commit log does not tell me when it broke,
> or why it broke, or who had their use case broken. Can you see
> why this is not acceptable?
>
> Please take the time to look at the traffic in netdev, and read
> the feedback given by maintainers on other patches, so that the
> common errors are understood by you, and not repeated. It
> will be time well spent!
>
Rick Jones has already well informed me the etiquettes off the list,
which I just broken.
Anyway, thanks for your time writing those suggestions.
> Thanks,
> Paul.
> ---
>
>> thanks
>>
>>
>>
>>
>>> btw, your email client wraps long lines..
>>>
>> Oh, I will definitely fix this.
>> thanks feng guang for the testing :)
>>
>>
>>
>>> Thanks,
>>> Fengguang
>>>
>>>> From a3f86ecc3ee16ff81d49416bbf791780422988b3 Mon Sep 17 00:00:00 2001
>>>> From: Fan Du<fan.du@...driver.com>
>>>> Date: Thu, 16 Aug 2012 17:31:25 +0800
>>>> Subject: [PATCH] Use rcu_dereference_bh to deference pointer
>>>> protected by rcu_read_lock_bh
>>>>
>>>> Signed-off-by: Fan Du<fan.du@...driver.com>
>>>> ---
>>>> net/xfrm/xfrm_policy.c | 2 +-
>>>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
>>>> index 5ad4d2c..75a9d6a 100644
>>>> --- a/net/xfrm/xfrm_policy.c
>>>> +++ b/net/xfrm/xfrm_policy.c
>>>> @@ -2501,7 +2501,7 @@ static void __net_init
>>>> xfrm_dst_ops_init(struct net *net)
>>>> struct xfrm_policy_afinfo *afinfo;
>>>>
>>>> rcu_read_lock_bh();
>>>> - afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET]);
>>>> + afinfo = rcu_dereference_bh(xfrm_policy_afinfo[AF_INET]);
>>>> if (afinfo)
>>>> net->xfrm.xfrm4_dst_ops = *afinfo->dst_ops;
>>>> #if IS_ENABLED(CONFIG_IPV6)
>>>> --
>>>> 1.7.1
>>>>
>>>>
>>>>
>>>>
>>>> On 2012年08月16日 15:37, Fengguang Wu wrote:
>>>>>
>>>>> Hi Priyanka,
>>>>>
>>>>> The below warning shows up, probably related to this commit:
>>>>>
>>>>> 418a99ac6ad487dc9c42e6b0e85f941af56330f2 Replace rwlock on
>>>>> xfrm_policy_afinfo with rcu
>>>>>
>>>>> [ 0.921216]
>>>>> [ 0.921645] ===============================
>>>>> [ 0.922766] [ INFO: suspicious RCU usage. ]
>>>>> [ 0.923887] 3.5.0-01540-g1669891 #64 Not tainted
>>>>> [ 0.925123] -------------------------------
>>>>> [ 0.932860] /c/kernel-tests/src/tip/net/xfrm/xfrm_policy.c:2504
>>>>> suspicious rcu_dereference_check() usage!
>>>>> [ 0.935361]
>>>>> [ 0.935361] other info that might help us debug this:
>>>>> [ 0.935361]
>>>>> [ 0.937472]
>>>>> [ 0.937472] rcu_scheduler_active = 1, debug_locks = 0
>>>>> [ 0.939182] 2 locks held by swapper/1:
>>>>> [ 0.940171] #0: (net_mutex){+.+.+.}, at: [<ffffffff814e1ad0>]
>>>>> register_pernet_subsys+0x21/0x57
>>>>> [ 0.942705] #1: (rcu_read_lock_bh){......}, at:
>>>>> [<ffffffff822c7329>] xfrm_net_init+0x1e4/0x437
>>>>> [ 0.951507]
>>>>> [ 0.951507] stack backtrace:
>>>>> [ 0.952660] Pid: 1, comm: swapper Not tainted 3.5.0-01540-g1669891
>>>>> #64
>>>>> [ 0.954364] Call Trace:
>>>>> [ 0.955074] [<ffffffff8108b375>] lockdep_rcu_suspicious+0x174/0x187
>>>>> [ 0.956736] [<ffffffff822c7453>] xfrm_net_init+0x30e/0x437
>>>>> [ 0.958205] [<ffffffff822c7329>] ? xfrm_net_init+0x1e4/0x437
>>>>> [ 0.959712] [<ffffffff814e134a>] ops_init+0x1bb/0x1ff
>>>>> [ 0.961067] [<ffffffff810861f9>] ? trace_hardirqs_on+0x1b/0x24
>>>>> [ 0.962644] [<ffffffff814e17cd>]
>>>>> register_pernet_operations.isra.5+0x9d/0xfe
>>>>> [ 0.971376] [<ffffffff814e1adf>] register_pernet_subsys+0x30/0x57
>>>>> [ 0.972992] [<ffffffff822c7130>] xfrm_init+0x17/0x2c
>>>>> [ 0.974316] [<ffffffff822c2f8c>] ip_rt_init+0x82/0xe7
>>>>> [ 0.975668] [<ffffffff822c31dc>] ip_init+0x10/0x25
>>>>> [ 0.976952] [<ffffffff822c3f77>] inet_init+0x235/0x360
>>>>> [ 0.978352] [<ffffffff822c3d42>] ? devinet_init+0xf2/0xf2
>>>>> [ 0.979808] [<ffffffff82283252>] do_one_initcall+0xb4/0x203
>>>>> [ 0.981313] [<ffffffff8228354a>] kernel_init+0x1a9/0x29a
>>>>> [ 0.982732] [<ffffffff822826d9>] ? loglevel+0x46/0x46
>>>>> [ 0.990889] [<ffffffff816d3d84>] kernel_thread_helper+0x4/0x10
>>>>> [ 0.992472] [<ffffffff816d262c>] ? retint_restore_args+0x13/0x13
>>>>> [ 0.994076] [<ffffffff822833a1>] ? do_one_initcall+0x203/0x203
>>>>> [ 0.995636] [<ffffffff816d3d80>] ? gs_change+0x13/0x13
>>>>> [ 0.997197] TCP established hash table entries: 8192 (order: 5,
>>>>> 131072 bytes)
>>>>> [ 1.000074] TCP bind hash table entries: 8192 (order: 7, 655360
>>>>> bytes)
>>>>>
>>>>> Thanks,
>>>>> Fengguang
>>>>
>>>>
>>>> --
>>>>
>>>> Love each day!
>>>> --fan
>>>
>>>
>>
>> --
>>
>> Love each day!
>> --fan
>
--
Love each day!
--fan
--
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