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SubjectRe: suspicious RCU usage in xfrm_net_init()

Hi, Fengguang

Could you please try the below patch, see if spewing still there?
thanks


From a3f86ecc3ee16ff81d49416bbf791780422988b3 Mon Sep 17 00:00:00 2001
From: Fan Du <fan.du@windriver.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@windriver.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
--
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