ratelimit.c 1.4 KB
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/*
 * ratelimit.c - Do something with rate limit.
 *
 * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
 *
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 * 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.
 *
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 * This file is released under the GPLv2.
 */

#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/module.h>

/*
 * __ratelimit - rate limiting
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 * @rs: ratelimit_state data
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 *
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 * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
 * in every @rs->ratelimit_jiffies
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 */
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int __ratelimit(struct ratelimit_state *rs)
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{
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	unsigned long flags;
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	int ret;
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	if (!rs->interval)
		return 1;
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	/*
	 * 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 (!spin_trylock_irqsave(&rs->lock, flags))
		return 1;

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	if (!rs->begin)
		rs->begin = jiffies;
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	if (time_is_before_jiffies(rs->begin + rs->interval)) {
		if (rs->missed)
			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
				__func__, rs->missed);
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		rs->begin   = 0;
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		rs->printed = 0;
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		rs->missed  = 0;
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	}
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	if (rs->burst && rs->burst > rs->printed) {
		rs->printed++;
		ret = 1;
	} else {
		rs->missed++;
		ret = 0;
	}
	spin_unlock_irqrestore(&rs->lock, flags);
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	return ret;
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}
EXPORT_SYMBOL(__ratelimit);