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Commit 152102c7 authored by Changli Gao's avatar Changli Gao Committed by David S. Miller
Browse files

rps: keep the old behavior on SMP without rps 



keep the old behavior on SMP without rps

RPS introduces a lock operation to per cpu variable input_pkt_queue on
SMP whenever rps is enabled or not. On SMP without RPS, this lock isn't
needed at all.

Signed-off-by: default avatarChangli Gao <xiaosuo@gmail.com>
----
net/core/dev.c | 42 ++++++++++++++++++++++++++++--------------
1 file changed, 28 insertions(+), 14 deletions(-)
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 630b943c

net/core/dev.c

+28 −14
Original line number Diff line number Diff line
@@ -206,6 +206,20 @@ static inline struct hlist_head *dev_index_hash(struct net *net, int ifindex) 
	return &net->dev_index_head[ifindex & (NETDEV_HASHENTRIES - 1)];

}



static inline void rps_lock(struct softnet_data *queue)

{

#ifdef CONFIG_RPS

	spin_lock(&queue->input_pkt_queue.lock);

#endif

}



static inline void rps_unlock(struct softnet_data *queue)

{

#ifdef CONFIG_RPS

	spin_unlock(&queue->input_pkt_queue.lock);

#endif

}



/* Device list insertion */

static int list_netdevice(struct net_device *dev)

{
@@ -2313,13 +2327,13 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu) 
	local_irq_save(flags);

	__get_cpu_var(netdev_rx_stat).total++;



	spin_lock(&queue->input_pkt_queue.lock);

	rps_lock(queue);

	if (queue->input_pkt_queue.qlen <= netdev_max_backlog) {

		if (queue->input_pkt_queue.qlen) {

enqueue:

			__skb_queue_tail(&queue->input_pkt_queue, skb);

			spin_unlock_irqrestore(&queue->input_pkt_queue.lock,

			    flags);

			rps_unlock(queue);

			local_irq_restore(flags);

			return NET_RX_SUCCESS;

		}
@@ -2341,7 +2355,7 @@ enqueue: 
		goto enqueue;

	}



	spin_unlock(&queue->input_pkt_queue.lock);

	rps_unlock(queue);



	__get_cpu_var(netdev_rx_stat).dropped++;

	local_irq_restore(flags);
@@ -2766,19 +2780,19 @@ int netif_receive_skb(struct sk_buff *skb) 
EXPORT_SYMBOL(netif_receive_skb);



/* Network device is going away, flush any packets still pending  */

static void flush_backlog(struct net_device *dev, int cpu)

static void flush_backlog(void *arg)

{

	struct softnet_data *queue = &per_cpu(softnet_data, cpu);

	struct net_device *dev = arg;

	struct softnet_data *queue = &__get_cpu_var(softnet_data);

	struct sk_buff *skb, *tmp;

	unsigned long flags;



	spin_lock_irqsave(&queue->input_pkt_queue.lock, flags);

	rps_lock(queue);

	skb_queue_walk_safe(&queue->input_pkt_queue, skb, tmp)

		if (skb->dev == dev) {

			__skb_unlink(skb, &queue->input_pkt_queue);

			kfree_skb(skb);

		}

	spin_unlock_irqrestore(&queue->input_pkt_queue.lock, flags);

	rps_unlock(queue);

}



static int napi_gro_complete(struct sk_buff *skb)
@@ -3091,14 +3105,16 @@ static int process_backlog(struct napi_struct *napi, int quota) 
	do {

		struct sk_buff *skb;



		spin_lock_irq(&queue->input_pkt_queue.lock);

		local_irq_disable();

		rps_lock(queue);

		skb = __skb_dequeue(&queue->input_pkt_queue);

		if (!skb) {

			__napi_complete(napi);

			spin_unlock_irq(&queue->input_pkt_queue.lock);

			break;

		}

		spin_unlock_irq(&queue->input_pkt_queue.lock);

		rps_unlock(queue);

		local_irq_enable();



		__netif_receive_skb(skb);

	} while (++work < quota && jiffies == start_time);
@@ -5548,7 +5564,6 @@ void netdev_run_todo(void) 
	while (!list_empty(&list)) {

		struct net_device *dev

			= list_first_entry(&list, struct net_device, todo_list);

		int i;

		list_del(&dev->todo_list);



		if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
@@ -5560,8 +5575,7 @@ void netdev_run_todo(void) 


		dev->reg_state = NETREG_UNREGISTERED;



		for_each_online_cpu(i)

			flush_backlog(dev, i);

		on_each_cpu(flush_backlog, dev, 1);



		netdev_wait_allrefs(dev);