netdev - [PATCH wpan-next v2 10/11] net: mac802154: Introduce a global device lock

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Date:   Fri, 26 Aug 2022 16:40:48 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH wpan-next v2 10/11] net: mac802154: Introduce a global device lock

The purpose of this device lock is to prevent the removal of the device
while an asynchronous MLME operation happens. The RTNL works well for
that but in a later series having the RTNL taken here will be
problematic and will cause lockdep to warn us about a circular
dependency. We don't really need the RTNL here, just a serialization
over this operation.

Replace the RTNL calls with this new lock.

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 net/mac802154/ieee802154_i.h |  2 ++
 net/mac802154/iface.c        |  4 ++++
 net/mac802154/main.c         |  1 +
 net/mac802154/tx.c           | 12 ++++++------
 4 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
index 010365a6364e..b8775bcc9003 100644
--- a/net/mac802154/ieee802154_i.h
+++ b/net/mac802154/ieee802154_i.h
@@ -29,7 +29,9 @@ struct ieee802154_local {
 	/* ieee802154 phy */
 	struct wpan_phy *phy;
 
+	/* Open/close counter and lock */
 	int open_count;
+	struct mutex device_lock;
 
 	/* As in mac80211 slaves list is modified:
 	 * 1) under the RTNL
diff --git a/net/mac802154/iface.c b/net/mac802154/iface.c
index 8467a629e21f..29af3f80b4d0 100644
--- a/net/mac802154/iface.c
+++ b/net/mac802154/iface.c
@@ -315,11 +315,15 @@ static int mac802154_slave_close(struct net_device *dev)
 
 	ASSERT_RTNL();
 
+	mutex_lock(&local->device_lock);
+
 	netif_stop_queue(dev);
 	local->open_count--;
 
 	clear_bit(SDATA_STATE_RUNNING, &sdata->state);
 
+	mutex_unlock(&local->device_lock);
+
 	if (!local->open_count)
 		ieee802154_stop_device(local);
 
diff --git a/net/mac802154/main.c b/net/mac802154/main.c
index 95100df6489a..7657fb46c9e1 100644
--- a/net/mac802154/main.c
+++ b/net/mac802154/main.c
@@ -90,6 +90,7 @@ ieee802154_alloc_hw(size_t priv_data_len, const struct ieee802154_ops *ops)
 
 	INIT_LIST_HEAD(&local->interfaces);
 	mutex_init(&local->iflist_mtx);
+	mutex_init(&local->device_lock);
 
 	tasklet_setup(&local->tasklet, ieee802154_tasklet_handler);
 
diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
index 9d8d43cf1e64..fb555797f326 100644
--- a/net/mac802154/tx.c
+++ b/net/mac802154/tx.c
@@ -143,14 +143,14 @@ int ieee802154_mlme_tx(struct ieee802154_local *local,
 {
 	int ret;
 
-	/* Avoid possible calls to ->ndo_stop() when we asynchronously perform
-	 * MLME transmissions.
+	/* Serialize possible calls to ->ndo_stop() when we asynchronously
+	 * perform MLME transmissions.
 	 */
-	rtnl_lock();
+	mutex_lock(&local->device_lock);
 
 	/* Ensure the device was not stopped, otherwise error out */
 	if (!local->open_count) {
-		rtnl_unlock();
+		mutex_unlock(&local->device_lock);
 		return -ENETDOWN;
 	}
 
@@ -158,14 +158,14 @@ int ieee802154_mlme_tx(struct ieee802154_local *local,
 	 * net interface expects this cannot happen.
 	 */
 	if (WARN_ON_ONCE(!netif_running(sdata->dev))) {
-		rtnl_unlock();
+		mutex_unlock(&local->device_lock);
 		return -ENETDOWN;
 	}
 
 	ieee802154_tx(local, skb);
 	ret = ieee802154_sync_queue(local);
 
-	rtnl_unlock();
+	mutex_unlock(&local->device_lock);
 
 	return ret;
 }
-- 
2.34.1