netdev - [PATCH wpan-next 06/11] net: mac802154: Hold the transmit queue when relevant

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Date:   Wed, 27 Apr 2022 18:46:54 +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>, 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 06/11] net: mac802154: Hold the transmit queue when relevant

Let's create a hold_txs atomic variable and increment/decrement it when
relevant. Currently we can use it during a suspend. Very soon we will
also use this feature during scans.

When the variable is incremented, any further wake up call will be
skipped until the variable gets decremented back.

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 include/net/cfg802154.h      |  3 ++-
 net/mac802154/cfg.c          |  2 ++
 net/mac802154/ieee802154_i.h | 24 ++++++++++++++++++++++++
 net/mac802154/tx.c           | 15 +++++++++++++++
 net/mac802154/util.c         |  3 +++
 5 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
index 473ebcb9b155..043d8e4359e7 100644
--- a/include/net/cfg802154.h
+++ b/include/net/cfg802154.h
@@ -214,8 +214,9 @@ struct wpan_phy {
 	/* the network namespace this phy lives in currently */
 	possible_net_t _net;
 
-	/* Transmission monitoring */
+	/* Transmission monitoring and control */
 	atomic_t ongoing_txs;
+	atomic_t hold_txs;
 
 	char priv[] __aligned(NETDEV_ALIGN);
 };
diff --git a/net/mac802154/cfg.c b/net/mac802154/cfg.c
index dafe02548161..0540a2b014d2 100644
--- a/net/mac802154/cfg.c
+++ b/net/mac802154/cfg.c
@@ -46,6 +46,7 @@ static int ieee802154_suspend(struct wpan_phy *wpan_phy)
 	if (!local->open_count)
 		goto suspend;
 
+	ieee802154_hold_queue(local);
 	ieee802154_stop_queue(local);
 	synchronize_net();
 
@@ -72,6 +73,7 @@ static int ieee802154_resume(struct wpan_phy *wpan_phy)
 		return ret;
 
 wake_up:
+	ieee802154_release_queue(local);
 	ieee802154_wake_queue(local);
 	local->suspended = false;
 	return 0;
diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
index 3f59a291b481..b55fdefb0b34 100644
--- a/net/mac802154/ieee802154_i.h
+++ b/net/mac802154/ieee802154_i.h
@@ -142,6 +142,30 @@ enum hrtimer_restart ieee802154_xmit_ifs_timer(struct hrtimer *timer);
  */
 void ieee802154_wake_queue(struct ieee802154_local *local);
 
+/**
+ * ieee802154_hold_queue - hold ieee802154 queue
+ * @local: main mac object
+ *
+ * Hold a queue, this queue cannot be woken up while this is active.
+ */
+void ieee802154_hold_queue(struct ieee802154_local *local);
+
+/**
+ * ieee802154_release_queue - release ieee802154 queue
+ * @local: main mac object
+ *
+ * Release a queue which is held. The queue can now be woken up.
+ */
+void ieee802154_release_queue(struct ieee802154_local *local);
+
+/**
+ * ieee802154_queue_is_held - checks whether the ieee802154 queue is held
+ * @local: main mac object
+ *
+ * Checks whether the queue is currently held.
+ */
+bool ieee802154_queue_is_held(struct ieee802154_local *local);
+
 /**
  * ieee802154_stop_queue - stop ieee802154 queue
  * @local: main mac object
diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
index 8c0bad7796ba..d088aa8119e8 100644
--- a/net/mac802154/tx.c
+++ b/net/mac802154/tx.c
@@ -106,6 +106,21 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
 	return NETDEV_TX_OK;
 }
 
+void ieee802154_hold_queue(struct ieee802154_local *local)
+{
+	atomic_inc(&local->phy->hold_txs);
+}
+
+void ieee802154_release_queue(struct ieee802154_local *local)
+{
+	atomic_dec(&local->phy->hold_txs);
+}
+
+bool ieee802154_queue_is_held(struct ieee802154_local *local)
+{
+	return atomic_read(&local->phy->hold_txs);
+}
+
 netdev_tx_t
 ieee802154_monitor_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
diff --git a/net/mac802154/util.c b/net/mac802154/util.c
index 4bcc9cd2eb9d..847e0864b575 100644
--- a/net/mac802154/util.c
+++ b/net/mac802154/util.c
@@ -17,6 +17,9 @@ void ieee802154_wake_queue(struct ieee802154_local *local)
 {
 	struct ieee802154_sub_if_data *sdata;
 
+	if (ieee802154_queue_is_held(local))
+		return;
+
 	rcu_read_lock();
 	list_for_each_entry_rcu(sdata, &local->interfaces, list) {
 		if (!sdata->dev)
-- 
2.27.0