[PATCH wpan-next 09/11] net: mac802154: Introduce a helper to disable the queue

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Alexander Aring <alex.aring@gmail.com>,
	Stefan Schmidt <stefan@datenfreihafen.org>,
	linux-wpan@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	netdev@vger.kernel.org, David Girault <david.girault@qorvo.com>,
	Romuald Despres <romuald.despres@qorvo.com>,
	Frederic Blain <frederic.blain@qorvo.com>,
	Nicolas Schodet <nico@ni.fr.eu.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>
Subject: [PATCH wpan-next 09/11] net: mac802154: Introduce a helper to disable the queue
Date: Wed, 27 Apr 2022 18:46:57 +0200	[thread overview]
Message-ID: <20220427164659.106447-10-miquel.raynal@bootlin.com> (raw)
In-Reply-To: <20220427164659.106447-1-miquel.raynal@bootlin.com>

Sometimes calling the stop queue helper is not enough because it does
not hold any lock. In order to be safe and avoid racy situations when
trying to (soon) sync the Tx queue, for instance before sending an MLME
frame, let's now introduce an helper which actually hold the necessary
locks when doing so.

Suggested-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 net/mac802154/ieee802154_i.h | 12 ++++++++++++
 net/mac802154/util.c         | 15 +++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
index cb61a4abaf37..c686a027555a 100644
--- a/net/mac802154/ieee802154_i.h
+++ b/net/mac802154/ieee802154_i.h
@@ -186,6 +186,18 @@ void ieee802154_stop_queue(struct ieee802154_local *local);
  */
 bool ieee802154_queue_is_stopped(struct ieee802154_local *local);
 
+/**
+ * ieee802154_disable_queue - disable ieee802154 queue
+ * @local: main mac object
+ *
+ * When trying to sync the Tx queue, we cannot just stop the queue
+ * (which is basically a bit being set without proper lock handling)
+ * because it would be racy. We actually need to call netif_tx_disable()
+ * instead, which is done by this helper. Restarting the queue can
+ * however still be done with a regular wake call.
+ */
+void ieee802154_disable_queue(struct ieee802154_local *local);
+
 /* MIB callbacks */
 void mac802154_dev_set_page_channel(struct net_device *dev, u8 page, u8 chan);
 
diff --git a/net/mac802154/util.c b/net/mac802154/util.c
index cfd17a7db532..3e2b157b34b1 100644
--- a/net/mac802154/util.c
+++ b/net/mac802154/util.c
@@ -62,6 +62,21 @@ bool ieee802154_queue_is_stopped(struct ieee802154_local *local)
 	return stopped;
 }
 
+void ieee802154_disable_queue(struct ieee802154_local *local)
+{
+        struct ieee802154_sub_if_data *sdata;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
+                if (!sdata->dev)
+                        continue;
+
+		netif_tx_disable(sdata->dev);
+        }
+        rcu_read_unlock();
+}
+EXPORT_SYMBOL(ieee802154_disable_queue);
+
 enum hrtimer_restart ieee802154_xmit_ifs_timer(struct hrtimer *timer)
 {
 	struct ieee802154_local *local =
-- 
2.27.0

