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mac802154: tx: fix synced xmit deadlock

PATCH Superseded Alexander Aring 1 participant 2 messages Dec 9, 2015

Subsystems (2)
Networking IEEE 802.15.4

v1 of 2 Superseded Latest is v2 →

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Alexander Aring

author maintainer
#0 lore raw

PATCH 1/1 mac802154: tx: fix synced xmit deadlock

This patch reverts 6001d52 ("mac802154: tx: don't allow if down while sync tx"). This has side effects with stop callback which flush the transmit workqueue. The stop callback will wait until the workqueue is flushed and holding the rtnl lock. That means it can happen that the stop callback waits forever because it try to lock the rtnl mutex which is already hold by stop callback.

Cc Michael Hennerich <[email protected]>
Signed-off-by Alexander Aring <[email protected]>
---
 net/mac802154/tx.c | 9 ---------
 1 file changed, 9 deletions(-)
net/mac802154/tx.c +0 -9
index 3827f35..7e25345 100644
@@ -38,12 +38,6 @@ void ieee802154_xmit_worker(struct work_struct *work)
 	struct net_device *dev = skb->dev;
 	int res;
 
-	rtnl_lock();
-
-	/* check if ifdown occurred while schedule */
-	if (!netif_running(dev))
-		goto err_tx;
-
 	res = drv_xmit_sync(local, skb);
 	if (res)
 		goto err_tx;

@@ -53,14 +47,11 @@ void ieee802154_xmit_worker(struct work_struct *work)
 	dev->stats.tx_packets++;
 	dev->stats.tx_bytes += skb->len;
 
-	rtnl_unlock();
-
 	return;
 
 err_tx:
 	/* Restart the netif queue on each sub_if_data object. */
 	ieee802154_wake_queue(&local->hw);
-	rtnl_unlock();
 	kfree_skb(skb);
 	netdev_dbg(dev, "transmission failed\n");
 }
Signature · 1 line
2.6.1
author maintainer
#1 lore raw

Hi Marcel,

Quoted 7 lines · Alexander Aring

This patch reverts 6001d52 ("mac802154: tx: don't allow if down while sync tx"). This has side effects with stop callback which flush the transmit workqueue. The stop callback will wait until the workqueue is flushed and holding the rtnl lock. That means it can happen that the stop callback waits forever because it try to lock the rtnl mutex which is already hold by stop callback.

wrong patch here, I will send a v2 which also remove the ASSERT_RTNL while synced xmit driver callback.

- Alex