Commit 29578624 authored by Olaf Kirch's avatar Olaf Kirch Committed by David S. Miller
Browse files

[NET]: Fix races in net_rx_action vs netpoll. 



Keep netpoll/poll_napi from messing with the poll_list.
Only net_rx_action is allowed to manipulate the list.

Signed-off-by: default avatarOlaf Kirch <olaf.kirch@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1fd05ba5

include/linux/netdevice.h

+10 −0
Original line number Diff line number Diff line
@@ -261,6 +261,8 @@ enum netdev_state_t 
	__LINK_STATE_LINKWATCH_PENDING,

	__LINK_STATE_DORMANT,

	__LINK_STATE_QDISC_RUNNING,

	/* Set by the netpoll NAPI code */

	__LINK_STATE_POLL_LIST_FROZEN,

};
@@ -1014,6 +1016,14 @@ static inline void netif_rx_complete(struct net_device *dev) 
{

	unsigned long flags;



#ifdef CONFIG_NETPOLL

	/* Prevent race with netpoll - yes, this is a kludge.

	 * But at least it doesn't penalize the non-netpoll

	 * code path. */

	if (test_bit(__LINK_STATE_POLL_LIST_FROZEN, &dev->state))

		return;

#endif



	local_irq_save(flags);

	__netif_rx_complete(dev);

	local_irq_restore(flags);

net/core/netpoll.c

+8 −0
Original line number Diff line number Diff line
@@ -124,6 +124,13 @@ static void poll_napi(struct netpoll *np) 
	if (test_bit(__LINK_STATE_RX_SCHED, &np->dev->state) &&

	    npinfo->poll_owner != smp_processor_id() &&

	    spin_trylock(&npinfo->poll_lock)) {

		/* When calling dev->poll from poll_napi, we may end up in

		 * netif_rx_complete. However, only the CPU to which the

		 * device was queued is allowed to remove it from poll_list.

		 * Setting POLL_LIST_FROZEN tells netif_rx_complete

		 * to leave the NAPI state alone.

		 */

		set_bit(__LINK_STATE_POLL_LIST_FROZEN, &np->dev->state);

		npinfo->rx_flags |= NETPOLL_RX_DROP;

		atomic_inc(&trapped);
@@ -131,6 +138,7 @@ static void poll_napi(struct netpoll *np) 


		atomic_dec(&trapped);

		npinfo->rx_flags &= ~NETPOLL_RX_DROP;

		clear_bit(__LINK_STATE_POLL_LIST_FROZEN, &np->dev->state);

		spin_unlock(&npinfo->poll_lock);

	}

}