Re: suspicious RCU usage in xfrm_net_init()

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:

quoted

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

quoted

 From a3f86ecc3ee16ff81d49416bbf791780422988b3 Mon Sep 17 00:00:00 2001
From: Fan Du<redacted>
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<redacted>
---
  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:

quoted

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