linux-kernel - [PATCH] net: wan: lapbether.c: Use built-in RCU list checking

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Message-Id: <20200115114101.13068-1-madhuparnabhowmik04@gmail.com>
Date:   Wed, 15 Jan 2020 17:11:01 +0530
From:   madhuparnabhowmik04@...il.com
To:     davem@...emloft.net, gregkh@...uxfoundation.org
Cc:     paulmck@...nel.org, joel@...lfernandes.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        frextrite@...il.com,
        Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>
Subject: [PATCH] net: wan: lapbether.c: Use built-in RCU list checking

From: Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>

The only callers of the function lapbeth_get_x25_dev()
are lapbeth_rcv() and lapbeth_device_event().

lapbeth_rcv() uses rcu_read_lock() whereas lapbeth_device_event()
is called with RTNL held (As mentioned in the comments).

Therefore, pass lockdep_rtnl_is_held() as cond argument in
list_for_each_entry_rcu();

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@...il.com>
---
 drivers/net/wan/lapbether.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
index 0f1217b506ad..e30d91a38cfb 100644
--- a/drivers/net/wan/lapbether.c
+++ b/drivers/net/wan/lapbether.c
@@ -64,7 +64,7 @@ static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
 {
 	struct lapbethdev *lapbeth;
 
-	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node) {
+	list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node, lockdep_rtnl_is_held()) {
 		if (lapbeth->ethdev == dev) 
 			return lapbeth;
 	}
-- 
2.17.1