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 	/* Paired with WRITE_ONCE() in .proc_handler().
31 	 * Changing two values seperately could be inconsistent
32 	 * and some message could be lost.  (See: net_ratelimit_state).
33 	 */
34 	int interval = READ_ONCE(rs->interval);
35 	int burst = READ_ONCE(rs->burst);
36 	unsigned long flags;
37 	int ret;
38 
39 	if (!interval)
40 		return 1;
41 
42 	/*
43 	 * If we contend on this state's lock then almost
44 	 * by definition we are too busy to print a message,
45 	 * in addition to the one that will be printed by
46 	 * the entity that is holding the lock already:
47 	 */
48 	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
49 		return 0;
50 
51 	if (!rs->begin)
52 		rs->begin = jiffies;
53 
54 	if (time_is_before_jiffies(rs->begin + interval)) {
55 		if (rs->missed) {
56 			if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
57 				printk_deferred(KERN_WARNING
58 						"%s: %d callbacks suppressed\n",
59 						func, rs->missed);
60 				rs->missed = 0;
61 			}
62 		}
63 		rs->begin   = jiffies;
64 		rs->printed = 0;
65 	}
66 	if (burst && burst > rs->printed) {
67 		rs->printed++;
68 		ret = 1;
69 	} else {
70 		rs->missed++;
71 		ret = 0;
72 	}
73 	raw_spin_unlock_irqrestore(&rs->lock, flags);
74 
75 	return ret;
76 }
77 EXPORT_SYMBOL(___ratelimit);
78