net/dev: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20161103145021.28528-9-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/cpuhotplug.h

@@ -36,6 +36,7 @@ enum cpuhp_state {
 	CPUHP_PERCPU_CNT_DEAD,
 	CPUHP_RADIX_DEAD,
 	CPUHP_PAGE_ALLOC_DEAD,
+	CPUHP_NET_DEV_DEAD,
 	CPUHP_WORKQUEUE_PREP,
 	CPUHP_POWER_NUMA_PREPARE,
 	CPUHP_HRTIMERS_PREPARE,

net/core/dev.c

@@ -7953,18 +7953,13 @@ out:
 }
 EXPORT_SYMBOL_GPL(dev_change_net_namespace);
 
-static int dev_cpu_callback(struct notifier_block *nfb,
-			    unsigned long action,
-			    void *ocpu)
+static int dev_cpu_dead(unsigned int oldcpu)
 {
 	struct sk_buff **list_skb;
 	struct sk_buff *skb;
-	unsigned int cpu, oldcpu = (unsigned long)ocpu;
+	unsigned int cpu;
 	struct softnet_data *sd, *oldsd;
 
-	if (action != CPU_DEAD && action != CPU_DEAD_FROZEN)
-		return NOTIFY_OK;
-
 	local_irq_disable();
 	cpu = smp_processor_id();
 	sd = &per_cpu(softnet_data, cpu);
@@ -8014,10 +8009,9 @@ static int dev_cpu_callback(struct notifier_block *nfb,
 		input_queue_head_incr(oldsd);
 	}
 
-	return NOTIFY_OK;
+	return 0;
 }
 
-
 /**
  *	netdev_increment_features - increment feature set by one
  *	@all: current feature set
@@ -8351,7 +8345,9 @@ static int __init net_dev_init(void)
 	open_softirq(NET_TX_SOFTIRQ, net_tx_action);
 	open_softirq(NET_RX_SOFTIRQ, net_rx_action);
 
-	hotcpu_notifier(dev_cpu_callback, 0);
+	rc = cpuhp_setup_state_nocalls(CPUHP_NET_DEV_DEAD, "net/dev:dead",
+				       NULL, dev_cpu_dead);
+	WARN_ON(rc < 0);
 	dst_subsys_init();
 	rc = 0;
 out: