Revert "[NET]: Fix races in net_rx_action vs netpoll."

This reverts commit 29578624e354f56143d92510fff33a8b2aaa2c03.

Ingo Molnar reports complete breakage with his e1000 card (no
networking, card reports transmit timeouts), and bisected it down to
this commit.  Let's figure out what went wrong, but not keep breaking
machines until we do.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Olaf Kirch <olaf.kirch@oracle.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/netdevice.h

@@ -262,8 +262,6 @@ 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,
 };
 
 
@@ -1022,14 +1020,6 @@ 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

@@ -124,13 +124,6 @@ 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);
 
@@ -138,7 +131,6 @@ 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);
 	}
 }