lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 15 Jul 2008 03:05:31 -0700 (PDT)
From:	David Miller <>
Subject: Re: TXQ real_num_tx_queues comments/questions

From: Johannes Berg <>
Date: Tue, 15 Jul 2008 11:49:09 +0200

> Yes, I think we can fix it by deferring the requeue to a workqueue,
> using synchronize_net() and putting RCU protection against the
> select_queue call.

I'm respinning my net-tx-2.6 tree at the moment and I'll
make patch 8 look like below.

When I get to the mac80211 bits I'll add the appropriate
synchronize_net() call.

netdev: Add netdev->select_queue() method.

Devices or device layers can set this to control the queue selection
performed by dev_pick_tx().

This function runs under RCU protection, which allows overriding
functions to have some way of synchronizing with things like dynamic
->real_num_tx_queues adjustments.

This makes the spinlock prefetch in dev_queue_xmit() a little bit
less effective, but that's the price right now for correctness.

Signed-off-by: David S. Miller <>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index fdac115..9464e64 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -724,6 +724,9 @@ struct net_device
 	void                    (*poll_controller)(struct net_device *dev);
+	u16			(*select_queue)(struct net_device *dev,
+						struct sk_buff *skb);
 	/* Network namespace this network device is inside */
 	struct net		*nd_net;
diff --git a/net/core/dev.c b/net/core/dev.c
index f027a1a..7ca9564 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1670,6 +1670,9 @@ static struct netdev_queue *dev_pick_tx(struct net_device *dev,
 	u16 queue_index = 0;
+	if (dev->select_queue)
+		queue_index = dev->select_queue(dev, skb);
 	skb_set_queue_mapping(skb, queue_index);
 	return netdev_get_tx_queue(dev, queue_index);
@@ -1710,14 +1713,14 @@ int dev_queue_xmit(struct sk_buff *skb)
-	txq = dev_pick_tx(dev, skb);
-	spin_lock_prefetch(&txq->lock);
 	/* Disable soft irqs for various locks below. Also
 	 * stops preemption for RCU.
+	txq = dev_pick_tx(dev, skb);
+	spin_lock_prefetch(&txq->lock);
 	/* Updates of qdisc are serialized by queue->lock.
 	 * The struct Qdisc which is pointed to by qdisc is now a
 	 * rcu structure - it may be accessed without acquiring
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists