1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * ratelimit.c - Do something with rate limit.
4  *
5  * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
6  *
7  * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
8  * parameter. Now every user can use their own standalone ratelimit_state.
9  */
10 
11 #include <linux/ratelimit.h>
12 #include <linux/jiffies.h>
13 #include <linux/export.h>
14 
15 /*
16  * __ratelimit - rate limiting
17  * @rs: ratelimit_state data
18  * @func: name of calling function
19  *
20  * This enforces a rate limit: not more than @rs->burst callbacks
21  * in every @rs->interval
22  *
23  * RETURNS:
24  * 0 means callbacks will be suppressed.
25  * 1 means go ahead and do it.
26  */
___ratelimit(struct ratelimit_state * rs,const char * func)27 int ___ratelimit(struct ratelimit_state *rs, const char *func)
28 {
29 	unsigned long flags;
30 	int ret;
31 
32 	if (!rs->interval)
33 		return 1;
34 
35 	/*
36 	 * If we contend on this state's lock then almost
37 	 * by definition we are too busy to print a message,
38 	 * in addition to the one that will be printed by
39 	 * the entity that is holding the lock already:
40 	 */
41 	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
42 		return 0;
43 
44 	if (!rs->begin)
45 		rs->begin = jiffies;
46 
47 	if (time_is_before_jiffies(rs->begin + rs->interval)) {
48 		if (rs->missed) {
49 			if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
50 				printk_deferred(KERN_WARNING
51 						"%s: %d callbacks suppressed\n",
52 						func, rs->missed);
53 				rs->missed = 0;
54 			}
55 		}
56 		rs->begin   = jiffies;
57 		rs->printed = 0;
58 	}
59 	if (rs->burst && rs->burst > rs->printed) {
60 		rs->printed++;
61 		ret = 1;
62 	} else {
63 		rs->missed++;
64 		ret = 0;
65 	}
66 	raw_spin_unlock_irqrestore(&rs->lock, flags);
67 
68 	return ret;
69 }
70 EXPORT_SYMBOL(___ratelimit);
71