[PATCH v3 24/41] net: mac802154: Hold the transmit queue when relevant

[Miquel Raynal <miquel.raynal@bootlin.com>]

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

When the variable is incremented, any further call to helpers usually
waking up the queue will skip this part because it is the core
responsibility to wake up the queue when relevant.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 include/net/cfg802154.h      | 3 ++-
 net/mac802154/cfg.c          | 4 +++-
 net/mac802154/ieee802154_i.h | 5 +++++
 net/mac802154/tx.c           | 7 +++++--
 net/mac802154/util.c         | 8 +++++++-
 5 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
index 969cae56b000..56aa672e1912 100644
--- a/include/net/cfg802154.h
+++ b/include/net/cfg802154.h
@@ -283,8 +283,9 @@ 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 1e4a9f74ed43..e8aabf215286 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;
 
+	atomic_inc(&wpan_phy->hold_txs);
 	ieee802154_stop_queue(&local->hw);
 	synchronize_net();
 
@@ -72,7 +73,8 @@ static int ieee802154_resume(struct wpan_phy *wpan_phy)
 		return ret;
 
 wake_up:
-	ieee802154_wake_queue(&local->hw);
+	if (!atomic_dec_and_test(&wpan_phy->hold_txs))
+		ieee802154_wake_queue(&local->hw);
 	local->suspended = false;
 	return 0;
 }
diff --git a/net/mac802154/ieee802154_i.h b/net/mac802154/ieee802154_i.h
index 18d1f6804810..0291e49058f2 100644
--- a/net/mac802154/ieee802154_i.h
+++ b/net/mac802154/ieee802154_i.h
@@ -190,6 +190,11 @@ void mac802154_unlock_table(struct net_device *dev);
 
 int mac802154_wpan_update_llsec(struct net_device *dev);
 
+static inline bool mac802154_queue_is_stopped(struct ieee802154_local *local)
+{
+	return atomic_read(&local->phy->hold_txs);
+}
+
 /* interface handling */
 int ieee802154_iface_init(void);
 void ieee802154_iface_exit(void);
diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
index 731e86bfe73f..a8d4d5e175b6 100644
--- a/net/mac802154/tx.c
+++ b/net/mac802154/tx.c
@@ -43,7 +43,9 @@ void ieee802154_xmit_sync_worker(struct work_struct *work)
 
 err_tx:
 	/* Restart the netif queue on each sub_if_data object. */
-	ieee802154_wake_queue(&local->hw);
+	if (!mac802154_queue_is_stopped(local))
+		ieee802154_wake_queue(&local->hw);
+
 	kfree_skb(skb);
 	atomic_dec(&local->phy->ongoing_txs);
 	netdev_dbg(dev, "transmission failed\n");
@@ -87,7 +89,8 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
 
 		ret = drv_xmit_async(local, skb);
 		if (ret) {
-			ieee802154_wake_queue(&local->hw);
+			if (!mac802154_queue_is_stopped(local))
+				ieee802154_wake_queue(&local->hw);
 			goto err_tx;
 		}
 
diff --git a/net/mac802154/util.c b/net/mac802154/util.c
index 0fa538b0debc..db2ac53b937e 100644
--- a/net/mac802154/util.c
+++ b/net/mac802154/util.c
@@ -56,8 +56,13 @@ enum hrtimer_restart ieee802154_xmit_ifs_timer(struct hrtimer *timer)
 void ieee802154_xmit_complete(struct ieee802154_hw *hw, struct sk_buff *skb,
 			      bool ifs_handling)
 {
+	struct ieee802154_local *local = hw_to_local(hw);
+
+	/* Avoid waking-up a queue which needs to remain stopped */
+	if (mac802154_queue_is_stopped(local))
+		goto after_wakeup;
+
 	if (ifs_handling) {
-		struct ieee802154_local *local = hw_to_local(hw);
 		u8 max_sifs_size;
 
 		/* If transceiver sets CRC on his own we need to use lifs
@@ -82,6 +87,7 @@ void ieee802154_xmit_complete(struct ieee802154_hw *hw, struct sk_buff *skb,
 		ieee802154_wake_queue(hw);
 	}
 
+after_wakeup:
 	dev_consume_skb_any(skb);
 	atomic_dec(&hw->phy->ongoing_txs);
 }
-- 
2.27.0