/*
   * ratelimit.c - Do something with rate limit.
   *
   * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
   *
   * This file is released under the GPLv2.
   *
   */
  
  #include <linux/kernel.h>
  #include <linux/jiffies.h>
  #include <linux/module.h>
  
  /*
   * __ratelimit - rate limiting
   * @ratelimit_jiffies: minimum time in jiffies between two callbacks
   * @ratelimit_burst: number of callbacks we do before ratelimiting
   *
   * This enforces a rate limit: not more than @ratelimit_burst callbacks
   * in every ratelimit_jiffies
   */
  int __ratelimit(int ratelimit_jiffies, int ratelimit_burst)
  {
  	static DEFINE_SPINLOCK(ratelimit_lock);
  	static unsigned toks = 10 * 5 * HZ;
  	static unsigned long last_msg;
  	static int missed;
  	unsigned long flags;
  	unsigned long now = jiffies;
  
  	spin_lock_irqsave(&ratelimit_lock, flags);
  	toks += now - last_msg;
  	last_msg = now;
  	if (toks > (ratelimit_burst * ratelimit_jiffies))
  		toks = ratelimit_burst * ratelimit_jiffies;
  	if (toks >= ratelimit_jiffies) {
  		int lost = missed;
  
  		missed = 0;
  		toks -= ratelimit_jiffies;
  		spin_unlock_irqrestore(&ratelimit_lock, flags);
  		if (lost)
  			printk(KERN_WARNING "%s: %d messages suppressed
  ",
  				__func__, lost);
  		return 1;
  	}
  	missed++;
  	spin_unlock_irqrestore(&ratelimit_lock, flags);
  	return 0;
  }
  EXPORT_SYMBOL(__ratelimit);