[PATCH] Hotplug CPUs: Other CPU_DEAD Notifiers

Various files keep per-cpu caches which need to be freed/moved when a
CPU goes down.  All under CONFIG_HOTPLUG_CPU ifdefs.

scsi.c: drain dead cpu's scsi_done_q onto this cpu.

buffer.c: brelse the bh_lrus queue for dead cpu.

timer.c: migrate timers from dead cpu, being careful of lock order vs
	__mod_timer.

radix_tree.c: free dead cpu's radix_tree_preloads

page_alloc.c: empty dead cpu's nr_pagecache_local into nr_pagecache, and
	free pages on cpu's local cache.

slab.c: stop reap_timer for dead cpu, adjust each cache's free limit, and
	free each slab cache's per-cpu block.

swap.c: drain dead cpu's lru_add_pvecs into ours, and empty its committed_space
	counter into global counter.

dev.c: drain device queues from dead cpu into this one.

flow.c: drain dead cpu's flow cache.

1 files changed, 48 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index b4418fb5eb25..201878db9853 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -76,6 +76,7 @@
 #include <asm/system.h>
 #include <asm/bitops.h>
 #include <linux/config.h>
+#include <linux/cpu.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
@@ -3131,6 +3132,52 @@ int unregister_netdevice(struct net_device *dev)
 	return 0;
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static int dev_cpu_callback(struct notifier_block *nfb,
+			    unsigned long action,
+			    void *ocpu)
+{
+	struct sk_buff **list_skb;
+	struct net_device **list_net;
+	struct sk_buff *skb;
+	unsigned int cpu, oldcpu = (unsigned long)ocpu;
+	struct softnet_data *sd, *oldsd;
+
+	if (action != CPU_DEAD)
+		return NOTIFY_OK;
+
+	local_irq_disable();
+	cpu = smp_processor_id();
+	sd = &per_cpu(softnet_data, cpu);
+	oldsd = &per_cpu(softnet_data, oldcpu);
+
+	/* Find end of our completion_queue. */
+	list_skb = &sd->completion_queue;
+	while (*list_skb)
+		list_skb = &(*list_skb)->next;
+	/* Append completion queue from offline CPU. */
+	*list_skb = oldsd->completion_queue;
+	oldsd->completion_queue = NULL;
+
+	/* Find end of our output_queue. */
+	list_net = &sd->output_queue;
+	while (*list_net)
+		list_net = &(*list_net)->next_sched;
+	/* Append output queue from offline CPU. */
+	*list_net = oldsd->output_queue;
+	oldsd->output_queue = NULL;
+
+	raise_softirq_irqoff(NET_TX_SOFTIRQ);
+	local_irq_enable();
+
+	/* Process offline CPU's input_pkt_queue */
+	while ((skb = __skb_dequeue(&oldsd->input_pkt_queue)))
+		netif_rx(skb);
+
+	return NOTIFY_OK;
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
 
 /*
  *	Initialize the DEV module. At boot time this walks the device list and
@@ -3195,6 +3242,7 @@ static int __init net_dev_init(void)
 	open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);
 	open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL);
 
+	hotcpu_notifier(dev_cpu_callback, 0);
 	dst_init();
 	dev_mcast_init();
 	rc = 0;