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/export.h>
15 
16 /*
17  * __ratelimit - rate limiting
18  * @rs: ratelimit_state data
19  * @func: name of calling function
20  *
21  * This enforces a rate limit: not more than @rs->burst callbacks
22  * in every @rs->interval
23  *
24  * RETURNS:
25  * 0 means callbacks will be suppressed.
26  * 1 means go ahead and do it.
27  */
___ratelimit(struct ratelimit_state * rs,const char * func)28 int ___ratelimit(struct ratelimit_state *rs, const char *func)
29 {
30 	unsigned long flags;
31 	int ret;
32 
33 	if (!rs->interval)
34 		return 1;
35 
36 	/*
37 	 * If we contend on this state's lock then almost
38 	 * by definition we are too busy to print a message,
39 	 * in addition to the one that will be printed by
40 	 * the entity that is holding the lock already:
41 	 */
42 	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
43 		return 0;
44 
45 	if (!rs->begin)
46 		rs->begin = jiffies;
47 
48 	if (time_is_before_jiffies(rs->begin + rs->interval)) {
49 		if (rs->missed) {
50 			if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
51 				printk_deferred(KERN_WARNING
52 						"%s: %d callbacks suppressed\n",
53 						func, rs->missed);
54 				rs->missed = 0;
55 			}
56 		}
57 		rs->begin   = jiffies;
58 		rs->printed = 0;
59 	}
60 	if (rs->burst && rs->burst > rs->printed) {
61 		rs->printed++;
62 		ret = 1;
63 	} else {
64 		rs->missed++;
65 		ret = 0;
66 	}
67 	raw_spin_unlock_irqrestore(&rs->lock, flags);
68 
69 	return ret;
70 }
71 EXPORT_SYMBOL(___ratelimit);
72