Patchwork net: Allocate RX and TX queues in alloc_netdev_mq

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Submitter Tom Herbert
Date Oct. 28, 2010, 5:45 p.m.
Message ID <alpine.DEB.1.00.1010281036350.22486@pokey.mtv.corp.google.com>
Download mbox | patch
Permalink /patch/69478/
State Rejected
Delegated to: David Miller
Headers show

Comments

Tom Herbert - Oct. 28, 2010, 5:45 p.m.
Both TX and RX queue allocations in the netdev structure had been moved
to register_device with the idea that the number of queues could be
changed between device allocation and registration.  It was determined
that changing the num_queues after the call to alloc_netdev_mq was not
a good idea, so that was abandoned.  Also, some drivers call
netif_queue_start without registering device, which causes panic
when dev->_tx queue structure is accessed.  This patch moves queue
allocations back to alloc_netdev_mq to fix these issues.

Signed-off-by: Tom Herbert <therbert@google.com>
---
 net/core/dev.c |   38 ++++++++++++++++++--------------------
 1 files changed, 18 insertions(+), 20 deletions(-)
David Miller - Oct. 28, 2010, 5:49 p.m.
From: Tom Herbert <therbert@google.com>
Date: Thu, 28 Oct 2010 10:45:45 -0700 (PDT)

> Both TX and RX queue allocations in the netdev structure had been moved
> to register_device with the idea that the number of queues could be
> changed between device allocation and registration.  It was determined
> that changing the num_queues after the call to alloc_netdev_mq was not
> a good idea, so that was abandoned.  Also, some drivers call
> netif_queue_start without registering device, which causes panic
> when dev->_tx queue structure is accessed.  This patch moves queue
> allocations back to alloc_netdev_mq to fix these issues.
> 
> Signed-off-by: Tom Herbert <therbert@google.com>

Changing the TX queue state with a netif_stop_queue() call or
similar was always completely pointless and frankly a bug.

So that should not influence the motivation behind this change
at all.

In fact I _like_ that it crashes now so that we are forced
to fix these cases.

Really, the queue state is absolutely immaterial during
device allocation and registration.  It's state is
%100 "don't care" until ->open() is invoked.

So any code that touches the queue state at these earlier points in
time is completely extraneous if not broken.
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Tom Herbert - Oct. 28, 2010, 6:08 p.m.
On Thu, Oct 28, 2010 at 10:49 AM, David Miller <davem@davemloft.net> wrote:
> From: Tom Herbert <therbert@google.com>
> Date: Thu, 28 Oct 2010 10:45:45 -0700 (PDT)
>
>> Both TX and RX queue allocations in the netdev structure had been moved
>> to register_device with the idea that the number of queues could be
>> changed between device allocation and registration.  It was determined
>> that changing the num_queues after the call to alloc_netdev_mq was not
>> a good idea, so that was abandoned.  Also, some drivers call
>> netif_queue_start without registering device, which causes panic
>> when dev->_tx queue structure is accessed.  This patch moves queue
>> allocations back to alloc_netdev_mq to fix these issues.
>>
>> Signed-off-by: Tom Herbert <therbert@google.com>
>
> Changing the TX queue state with a netif_stop_queue() call or
> similar was always completely pointless and frankly a bug.
>
> So that should not influence the motivation behind this change
> at all.
>
> In fact I _like_ that it crashes now so that we are forced
> to fix these cases.
>
> Really, the queue state is absolutely immaterial during
> device allocation and registration.  It's state is
> %100 "don't care" until ->open() is invoked.
>
> So any code that touches the queue state at these earlier points in
> time is completely extraneous if not broken.
>
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David Miller - Oct. 28, 2010, 6:10 p.m.
Did you mean to actually say something other than quoting everything
said so far? :-)

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Tom Herbert - Oct. 28, 2010, 6:11 p.m.
On Thu, Oct 28, 2010 at 11:10 AM, David Miller <davem@davemloft.net> wrote:
>
> Did you mean to actually say something other than quoting everything
> said so far? :-)
>
You're response was so nicely worded that I had to repeat it :-)

Anyway, thanks for the clarification!

>
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Patch

diff --git a/net/core/dev.c b/net/core/dev.c
index b2269ac..1f729d6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5009,10 +5009,10 @@  void netif_stacked_transfer_operstate(const struct net_device *rootdev,
 }
 EXPORT_SYMBOL(netif_stacked_transfer_operstate);
 
-static int netif_alloc_rx_queues(struct net_device *dev)
+static int netif_alloc_rx_queues(struct net_device *dev, int count)
 {
 #ifdef CONFIG_RPS
-	unsigned int i, count = dev->num_rx_queues;
+	int i;
 	struct netdev_rx_queue *rx;
 
 	BUG_ON(count < 1);
@@ -5030,13 +5030,15 @@  static int netif_alloc_rx_queues(struct net_device *dev)
 	 */
 	for (i = 0; i < count; i++)
 		rx[i].first = rx;
+
+	dev->num_rx_queues = count;
+	dev->real_num_rx_queues = count;
 #endif
 	return 0;
 }
 
-static int netif_alloc_netdev_queues(struct net_device *dev)
+static int netif_alloc_netdev_queues(struct net_device *dev, int count)
 {
-	unsigned int count = dev->num_tx_queues;
 	struct netdev_queue *tx;
 
 	BUG_ON(count < 1);
@@ -5048,6 +5050,10 @@  static int netif_alloc_netdev_queues(struct net_device *dev)
 		return -ENOMEM;
 	}
 	dev->_tx = tx;
+
+	dev->num_tx_queues = count;
+	dev->real_num_tx_queues = count;
+
 	return 0;
 }
 
@@ -5105,14 +5111,6 @@  int register_netdevice(struct net_device *dev)
 
 	dev->iflink = -1;
 
-	ret = netif_alloc_rx_queues(dev);
-	if (ret)
-		goto out;
-
-	ret = netif_alloc_netdev_queues(dev);
-	if (ret)
-		goto out;
-
 	netdev_init_queues(dev);
 
 	/* Init, if this function is available */
@@ -5558,6 +5556,12 @@  struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
 	dev = PTR_ALIGN(p, NETDEV_ALIGN);
 	dev->padded = (char *)dev - (char *)p;
 
+	if (netif_alloc_netdev_queues(dev, queue_count))
+		goto free_p;
+	
+	if (netif_alloc_rx_queues(dev, queue_count))
+		goto free_p;
+
 	dev->pcpu_refcnt = alloc_percpu(int);
 	if (!dev->pcpu_refcnt)
 		goto free_p;
@@ -5570,14 +5574,6 @@  struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
 
 	dev_net_set(dev, &init_net);
 
-	dev->num_tx_queues = queue_count;
-	dev->real_num_tx_queues = queue_count;
-
-#ifdef CONFIG_RPS
-	dev->num_rx_queues = queue_count;
-	dev->real_num_rx_queues = queue_count;
-#endif
-
 	dev->gso_max_size = GSO_MAX_SIZE;
 
 	INIT_LIST_HEAD(&dev->ethtool_ntuple_list.list);
@@ -5593,6 +5589,8 @@  struct net_device *alloc_netdev_mq(int sizeof_priv, const char *name,
 free_pcpu:
 	free_percpu(dev->pcpu_refcnt);
 free_p:
+	kfree(dev->_tx);
+	kfree(dev->_rx);
 	kfree(p);
 	return NULL;
 }