Subject: Re: suspicious RCU usage in xfrm_net_init()

From: Fan Du <[email-masked]>
Date: Fri, 17 Aug 2012 09:07:04 +0800

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?
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<[email-masked]>
>> 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<[email-masked]>
>> ---
>>   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
>>From f3b4d84f7ca2ed235c8c8ae5186f45e20b9b80db Mon Sep 17 00:00:00 2001
From: Fan Du <[email-masked]>
Date: Thu, 16 Aug 2012 17:51:25 +0800
Subject: [PATCH] Use rcu_dereference_bh to deference pointer protected by rcu_read_lock_bh

Signed-off-by: Fan Du <[email-masked]>
---
 net/xfrm/xfrm_policy.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 5ad4d2c..6405764 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2501,11 +2501,11 @@ 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)
-	afinfo = rcu_dereference(xfrm_policy_afinfo[AF_INET6]);
+	afinfo = rcu_dereference_bh(xfrm_policy_afinfo[AF_INET6]);
 	if (afinfo)
 		net->xfrm.xfrm6_dst_ops = *afinfo->dst_ops;
 #endif
-- 
1.7.1