/*
   * ratelimit.c - Do something with rate limit.
   *
   * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
   *
   * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
   * parameter. Now every user can use their own standalone ratelimit_state.
   *
   * This file is released under the GPLv2.
   */
  
  #include <linux/ratelimit.h>
  #include <linux/jiffies.h>
  #include <linux/export.h>
  
  /*
   * __ratelimit - rate limiting
   * @rs: ratelimit_state data
   * @func: name of calling function
   *
   * This enforces a rate limit: not more than @rs->burst callbacks
   * in every @rs->interval
   *
   * RETURNS:
   * 0 means callbacks will be suppressed.
   * 1 means go ahead and do it.
   */
  int ___ratelimit(struct ratelimit_state *rs, const char *func)
  {
  	unsigned long flags;
  	int ret;
  
  	if (!rs->interval)
  		return 1;
  
  	/*
  	 * If we contend on this state's lock then almost
  	 * by definition we are too busy to print a message,
  	 * in addition to the one that will be printed by
  	 * the entity that is holding the lock already:
  	 */
  	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
  		return 0;
  
  	if (!rs->begin)
  		rs->begin = jiffies;
  
  	if (time_is_before_jiffies(rs->begin + rs->interval)) {
  		if (rs->missed)
  			printk(KERN_WARNING "%s: %d callbacks suppressed
  ",
  				func, rs->missed);
  		rs->begin   = 0;
  		rs->printed = 0;
  		rs->missed  = 0;
  	}
  	if (rs->burst && rs->burst > rs->printed) {
  		rs->printed++;
  		ret = 1;
  	} else {
  		rs->missed++;
  		ret = 0;
  	}
  	raw_spin_unlock_irqrestore(&rs->lock, flags);
  
  	return ret;
  }
  EXPORT_SYMBOL(___ratelimit);