netdev - [PATCH] rebalance locks by converting write_lock_bh to write_lock+local_bh

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Message-ID: <20131121235402.GA11774@opentech.at>
Date:	Fri, 22 Nov 2013 00:54:02 +0100
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Alexey Kuznetsov <kuznet@....inr.ac.ru>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Pedro Roque <roque@...fc.ul.pt>,
	Peter Zijlstra <peterz@...radead.org>, netdev@...r.kernel.org
Subject: [PATCH] rebalance locks by converting write_lock_bh to
	write_lock+local_bh_disable

>From 2c8e669b691b825c0ed2a02bd7a698d8ed5c6d29 Mon Sep 17 00:00:00 2001
From: Nicholas Mc Guire <der.herr@...r.at>
Date: Thu, 21 Nov 2013 18:22:55 -0500
Subject: [PATCH] rebalance locks by converting write_lock_bh to write_lock+local_bh_disable
 

 in __neigh_event_send write_lock_bh(&neigh->lock) is implicitly balanced by
 write_unlock(&neigh->lock)+local_bh_disable() - while this is equivalent with
 respect to the effective low level locking primitives it breaks balancing
 in the locking api. This makes automatic lock-checking trigger false 
 positives, creates an implicit dependency between *_lock_bh and *_lock 
 functions as well as making the extremly simply locking of net core even
 easier to understand.

 The api inbalance was introduced in:
 commit cd28ca0a3dd17c68d24b839602a0e6268ad28b5d
 Author: Eric Dumazet <eric.dumazet@...il.com>
 This patch just rebalances the lock api

 No change of functionality

Signed-off-by: Nicholas Mc Guire <der.herr@...r.at>
---
 net/core/neighbour.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index ca15f32..d681c75 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -966,7 +966,8 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
 	int rc;
 	bool immediate_probe = false;
 
-	write_lock_bh(&neigh->lock);
+	local_bh_disable();
+	write_lock(&neigh->lock);
 
 	rc = 0;
 	if (neigh->nud_state & (NUD_CONNECTED | NUD_DELAY | NUD_PROBE))
-- 
1.7.2.5

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