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
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