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Dave Young5f97a5a2008-04-29 00:59:43 -07001/*
2 * ratelimit.c - Do something with rate limit.
3 *
4 * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
5 *
6 * This file is released under the GPLv2.
7 *
8 */
9
10#include <linux/kernel.h>
11#include <linux/jiffies.h>
12#include <linux/module.h>
13
14/*
15 * __ratelimit - rate limiting
16 * @ratelimit_jiffies: minimum time in jiffies between two callbacks
17 * @ratelimit_burst: number of callbacks we do before ratelimiting
18 *
19 * This enforces a rate limit: not more than @ratelimit_burst callbacks
20 * in every ratelimit_jiffies
21 */
22int __ratelimit(int ratelimit_jiffies, int ratelimit_burst)
23{
24 static DEFINE_SPINLOCK(ratelimit_lock);
25 static unsigned toks = 10 * 5 * HZ;
26 static unsigned long last_msg;
27 static int missed;
28 unsigned long flags;
29 unsigned long now = jiffies;
30
31 spin_lock_irqsave(&ratelimit_lock, flags);
32 toks += now - last_msg;
33 last_msg = now;
34 if (toks > (ratelimit_burst * ratelimit_jiffies))
35 toks = ratelimit_burst * ratelimit_jiffies;
36 if (toks >= ratelimit_jiffies) {
37 int lost = missed;
38
39 missed = 0;
40 toks -= ratelimit_jiffies;
41 spin_unlock_irqrestore(&ratelimit_lock, flags);
42 if (lost)
43 printk(KERN_WARNING "%s: %d messages suppressed\n",
44 __func__, lost);
45 return 1;
46 }
47 missed++;
48 spin_unlock_irqrestore(&ratelimit_lock, flags);
49 return 0;
50}
51EXPORT_SYMBOL(__ratelimit);