#include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/once.h>
  #include <linux/random.h>

  struct once_work {

  	struct work_struct work;
  	struct static_key *key;
  };

  static void once_deferred(struct work_struct *w)

  {

  	struct once_work *work;

  	work = container_of(w, struct once_work, work);

  	BUG_ON(!static_key_enabled(work->key));
  	static_key_slow_dec(work->key);
  	kfree(work);
  }

  static void once_disable_jump(struct static_key *key)

  {

  	struct once_work *w;

  
  	w = kmalloc(sizeof(*w), GFP_ATOMIC);
  	if (!w)
  		return;

  	INIT_WORK(&w->work, once_deferred);

  	w->key = key;
  	schedule_work(&w->work);
  }

  static DEFINE_SPINLOCK(once_lock);

  bool __do_once_start(bool *done, unsigned long *flags)
  	__acquires(once_lock)
  {
  	spin_lock_irqsave(&once_lock, *flags);

  	if (*done) {

  		spin_unlock_irqrestore(&once_lock, *flags);
  		/* Keep sparse happy by restoring an even lock count on
  		 * this lock. In case we return here, we don't call into
  		 * __do_once_done but return early in the DO_ONCE() macro.
  		 */
  		__acquire(once_lock);

  		return false;
  	}

  	return true;
  }

  EXPORT_SYMBOL(__do_once_start);
  
  void __do_once_done(bool *done, struct static_key *once_key,
  		    unsigned long *flags)
  	__releases(once_lock)
  {
  	*done = true;
  	spin_unlock_irqrestore(&once_lock, *flags);
  	once_disable_jump(once_key);
  }
  EXPORT_SYMBOL(__do_once_done);