netdev - [PATCH] net: caif: Add lockdep expression to RCU traversal primitive

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Date:   Thu, 12 Mar 2020 11:04:20 +0530
From:   Amol Grover <frextrite@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Richard Fontana <rfontana@...hat.com>,
        Allison Randal <allison@...utok.net>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Joel Fernandes <joel@...lfernandes.org>,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        "Paul E . Mckenney" <paulmck@...nel.org>,
        Amol Grover <frextrite@...il.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] net: caif: Add lockdep expression to RCU traversal primitive

caifdevs->list is traversed using list_for_each_entry_rcu()
outside an RCU read-side critical section but under the
protection of rtnl_mutex. Hence, add the corresponding lockdep
expression to silence the following false-positive warning:

[   10.868467] =============================
[   10.869082] WARNING: suspicious RCU usage
[   10.869817] 5.6.0-rc1-00177-g06ec0a154aae4 #1 Not tainted
[   10.870804] -----------------------------
[   10.871557] net/caif/caif_dev.c:115 RCU-list traversed in non-reader section!!

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Amol Grover <frextrite@...il.com>
---
 net/caif/caif_dev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/caif/caif_dev.c b/net/caif/caif_dev.c
index 03c7cdd8e4cb..195d2d67be8a 100644
--- a/net/caif/caif_dev.c
+++ b/net/caif/caif_dev.c
@@ -112,7 +112,8 @@ static struct caif_device_entry *caif_get(struct net_device *dev)
 	    caif_device_list(dev_net(dev));
 	struct caif_device_entry *caifd;
 
-	list_for_each_entry_rcu(caifd, &caifdevs->list, list) {
+	list_for_each_entry_rcu(caifd, &caifdevs->list, list,
+				lockdep_rtnl_is_held()) {
 		if (caifd->netdev == dev)
 			return caifd;
 	}
-- 
2.25.1