xref: /openbmc/linux/lib/ratelimit.c (revision f5c27da4)
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  */
27 int ___ratelimit(struct ratelimit_state *rs, const char *func)
28 {
29 	/* Paired with WRITE_ONCE() in .proc_handler().
30 	 * Changing two values seperately could be inconsistent
31 	 * and some message could be lost.  (See: net_ratelimit_state).
32 	 */
33 	int interval = READ_ONCE(rs->interval);
34 	int burst = READ_ONCE(rs->burst);
35 	unsigned long flags;
36 	int ret;
37 
38 	if (!interval)
39 		return 1;
40 
41 	/*
42 	 * If we contend on this state's lock then almost
43 	 * by definition we are too busy to print a message,
44 	 * in addition to the one that will be printed by
45 	 * the entity that is holding the lock already:
46 	 */
47 	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
48 		return 0;
49 
50 	if (!rs->begin)
51 		rs->begin = jiffies;
52 
53 	if (time_is_before_jiffies(rs->begin + interval)) {
54 		if (rs->missed) {
55 			if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
56 				printk_deferred(KERN_WARNING
57 						"%s: %d callbacks suppressed\n",
58 						func, rs->missed);
59 				rs->missed = 0;
60 			}
61 		}
62 		rs->begin   = jiffies;
63 		rs->printed = 0;
64 	}
65 	if (burst && burst > rs->printed) {
66 		rs->printed++;
67 		ret = 1;
68 	} else {
69 		rs->missed++;
70 		ret = 0;
71 	}
72 	raw_spin_unlock_irqrestore(&rs->lock, flags);
73 
74 	return ret;
75 }
76 EXPORT_SYMBOL(___ratelimit);
77