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Commit 53fb95d3 authored by Matt Mackall's avatar Matt Mackall Committed by David S. Miller
Browse files

[NETPOLL]: fix initialization/NAPI race 



This fixes a race during initialization with the NAPI softirq
processing by using an RCU approach.

This race was discovered when refill_skbs() was added to
the setup code.

Signed-off-by: default avatarMatt Mackall <mpm@selenic.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 26520765

include/linux/netpoll.h

+13 −6
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 


#include <linux/netdevice.h>

#include <linux/interrupt.h>

#include <linux/rcupdate.h>

#include <linux/list.h>



struct netpoll;
@@ -61,25 +62,31 @@ static inline int netpoll_rx(struct sk_buff *skb) 
	return ret;

}



static inline void netpoll_poll_lock(struct net_device *dev)

static inline void *netpoll_poll_lock(struct net_device *dev)

{

	rcu_read_lock(); /* deal with race on ->npinfo */

	if (dev->npinfo) {

		spin_lock(&dev->npinfo->poll_lock);

		dev->npinfo->poll_owner = smp_processor_id();

		return dev->npinfo;

	}

	return NULL;

}



static inline void netpoll_poll_unlock(struct net_device *dev)

static inline void netpoll_poll_unlock(void *have)

{

	if (dev->npinfo) {

		dev->npinfo->poll_owner = -1;

		spin_unlock(&dev->npinfo->poll_lock);

	struct netpoll_info *npi = have;



	if (npi) {

		npi->poll_owner = -1;

		spin_unlock(&npi->poll_lock);

	}

	rcu_read_unlock();

}



#else

#define netpoll_rx(a) 0

#define netpoll_poll_lock(a)

#define netpoll_poll_lock(a) 0

#define netpoll_poll_unlock(a)

#endif

net/core/dev.c

+5 −4
Original line number Diff line number Diff line
@@ -1696,6 +1696,7 @@ static void net_rx_action(struct softirq_action *h) 
	struct softnet_data *queue = &__get_cpu_var(softnet_data);

	unsigned long start_time = jiffies;

	int budget = netdev_budget;

	void *have;



	local_irq_disable();
@@ -1709,10 +1710,10 @@ static void net_rx_action(struct softirq_action *h) 


		dev = list_entry(queue->poll_list.next,

				 struct net_device, poll_list);

		netpoll_poll_lock(dev);

		have = netpoll_poll_lock(dev);



		if (dev->quota <= 0 || dev->poll(dev, &budget)) {

			netpoll_poll_unlock(dev);

			netpoll_poll_unlock(have);

			local_irq_disable();

			list_del(&dev->poll_list);

			list_add_tail(&dev->poll_list, &queue->poll_list);
@@ -1721,7 +1722,7 @@ static void net_rx_action(struct softirq_action *h) 
			else

				dev->quota = dev->weight;

		} else {

			netpoll_poll_unlock(dev);

			netpoll_poll_unlock(have);

			dev_put(dev);

			local_irq_disable();

		}

net/core/netpoll.c

+3 −0
Original line number Diff line number Diff line
@@ -732,6 +732,9 @@ int netpoll_setup(struct netpoll *np) 
	/* last thing to do is link it to the net device structure */

	ndev->npinfo = npinfo;



	/* avoid racing with NAPI reading npinfo */

	synchronize_rcu();



	return 0;



 release: