netdev - [PATCH wpan-next v4 07/11] net: mac802154: Introduce a helper to disable the queue

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Date:   Thu, 19 May 2022 17:05:12 +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 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>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH wpan-next v4 07/11] net: mac802154: Introduce a helper to disable the queue

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@...il.com>
Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 net/mac802154/ieee802154_i.h | 12 ++++++++++++
 net/mac802154/util.c         | 14 ++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
index 0c7ff9e0b632..e34db1d49ef4 100644
--- a/net/mac802154/ieee802154_i.h
+++ b/net/mac802154/ieee802154_i.h
@@ -149,6 +149,18 @@ void ieee802154_hold_queue(struct ieee802154_local *local);
  */
 void ieee802154_release_queue(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 0ed8b5bcbe8a..999534f64485 100644
--- a/net/mac802154/util.c
+++ b/net/mac802154/util.c
@@ -83,6 +83,20 @@ void ieee802154_release_queue(struct ieee802154_local *local)
 	spin_unlock_irqrestore(&local->phy->queue_lock, flags);
 }
 
+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();
+}
+
 enum hrtimer_restart ieee802154_xmit_ifs_timer(struct hrtimer *timer)
 {
 	struct ieee802154_local *local =
-- 
2.34.1