linux-kernel - [ 45/95] net/802/mrp: fix lockdep splat

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Message-Id: <20130625182158.733828365@linuxfoundation.org>
Date:	Tue, 25 Jun 2013 11:32:32 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Denys Fedoryshchenko <denys@...p.net.lb>,
	Eric Dumazet <edumazet@...gle.com>,
	David Ward <david.ward@...mit.edu>,
	Cong Wang <amwang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 45/95] net/802/mrp: fix lockdep splat

3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit faff57a92ba1d7247c5e86ecea2886d2c9d54507 ]

commit fb745e9a037895 ("net/802/mrp: fix possible race condition when
calling mrp_pdu_queue()") introduced a lockdep splat.

[   19.735147] =================================
[   19.735235] [ INFO: inconsistent lock state ]
[   19.735324] 3.9.2-build-0063 #4 Not tainted
[   19.735412] ---------------------------------
[   19.735500] inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
[   19.735592] rmmod/1840 [HC0[0]:SC0[0]:HE1:SE1] takes:
[   19.735682]  (&(&app->lock)->rlock#2){+.?...}, at: [<f862bb5b>]
mrp_uninit_applicant+0x69/0xba [mrp]

app->lock is normally taken under softirq context, so disable BH to
avoid the splat.

Reported-by: Denys Fedoryshchenko <denys@...p.net.lb>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: David Ward <david.ward@...mit.edu>
Cc: Cong Wang <amwang@...hat.com>
Tested-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/802/mrp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/802/mrp.c
+++ b/net/802/mrp.c
@@ -871,10 +871,10 @@ void mrp_uninit_applicant(struct net_dev
 	 */
 	del_timer_sync(&app->join_timer);
 
-	spin_lock(&app->lock);
+	spin_lock_bh(&app->lock);
 	mrp_mad_event(app, MRP_EVENT_TX);
 	mrp_pdu_queue(app);
-	spin_unlock(&app->lock);
+	spin_unlock_bh(&app->lock);
 
 	mrp_queue_xmit(app);
 


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