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 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);