xref: /openbmc/linux/lib/ratelimit.c (revision b6dcefde)
1 /*
2  * ratelimit.c - Do something with rate limit.
3  *
4  * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
5  *
6  * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
7  * parameter. Now every user can use their own standalone ratelimit_state.
8  *
9  * This file is released under the GPLv2.
10  */
11 
12 #include <linux/ratelimit.h>
13 #include <linux/jiffies.h>
14 #include <linux/module.h>
15 
16 /*
17  * __ratelimit - rate limiting
18  * @rs: ratelimit_state data
19  *
20  * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
21  * in every @rs->ratelimit_jiffies
22  */
23 int ___ratelimit(struct ratelimit_state *rs, const char *func)
24 {
25 	unsigned long flags;
26 	int ret;
27 
28 	if (!rs->interval)
29 		return 1;
30 
31 	/*
32 	 * If we contend on this state's lock then almost
33 	 * by definition we are too busy to print a message,
34 	 * in addition to the one that will be printed by
35 	 * the entity that is holding the lock already:
36 	 */
37 	if (!spin_trylock_irqsave(&rs->lock, flags))
38 		return 1;
39 
40 	if (!rs->begin)
41 		rs->begin = jiffies;
42 
43 	if (time_is_before_jiffies(rs->begin + rs->interval)) {
44 		if (rs->missed)
45 			printk(KERN_WARNING "%s: %d callbacks suppressed\n",
46 				func, rs->missed);
47 		rs->begin   = 0;
48 		rs->printed = 0;
49 		rs->missed  = 0;
50 	}
51 	if (rs->burst && rs->burst > rs->printed) {
52 		rs->printed++;
53 		ret = 1;
54 	} else {
55 		rs->missed++;
56 		ret = 0;
57 	}
58 	spin_unlock_irqrestore(&rs->lock, flags);
59 
60 	return ret;
61 }
62 EXPORT_SYMBOL(___ratelimit);
63