/*
   * CPU notifier helper code for blk-mq
   *
   * Copyright (C) 2013-2014 Jens Axboe
   */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/blkdev.h>
  #include <linux/list.h>
  #include <linux/llist.h>
  #include <linux/smp.h>
  #include <linux/cpu.h>
  
  #include <linux/blk-mq.h>
  #include "blk-mq.h"
  
  static LIST_HEAD(blk_mq_cpu_notify_list);
  static DEFINE_SPINLOCK(blk_mq_cpu_notify_lock);
  
  static int blk_mq_main_cpu_notify(struct notifier_block *self,
  				  unsigned long action, void *hcpu)
  {
  	unsigned int cpu = (unsigned long) hcpu;
  	struct blk_mq_cpu_notifier *notify;
  	int ret = NOTIFY_OK;
  
  	if (action != CPU_POST_DEAD)
  		return NOTIFY_OK;
  
  	spin_lock(&blk_mq_cpu_notify_lock);
  
  	list_for_each_entry(notify, &blk_mq_cpu_notify_list, list) {
  		ret = notify->notify(notify->data, action, cpu);
  		if (ret != NOTIFY_OK)
  			break;
  	}
  
  	spin_unlock(&blk_mq_cpu_notify_lock);
  	return ret;
  }
  
  void blk_mq_register_cpu_notifier(struct blk_mq_cpu_notifier *notifier)
  {
  	BUG_ON(!notifier->notify);
  
  	spin_lock(&blk_mq_cpu_notify_lock);
  	list_add_tail(&notifier->list, &blk_mq_cpu_notify_list);
  	spin_unlock(&blk_mq_cpu_notify_lock);
  }
  
  void blk_mq_unregister_cpu_notifier(struct blk_mq_cpu_notifier *notifier)
  {
  	spin_lock(&blk_mq_cpu_notify_lock);
  	list_del(&notifier->list);
  	spin_unlock(&blk_mq_cpu_notify_lock);
  }
  
  void blk_mq_init_cpu_notifier(struct blk_mq_cpu_notifier *notifier,
  			      int (*fn)(void *, unsigned long, unsigned int),
  			      void *data)
  {
  	notifier->notify = fn;
  	notifier->data = data;
  }
  
  void __init blk_mq_cpu_init(void)
  {
  	hotcpu_notifier(blk_mq_main_cpu_notify, 0);
  }