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 */
27int ___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 = 0;
37
38 /*
39 * Zero interval says never limit, otherwise, non-positive burst
40 * says always limit.
41 */
42 if (interval <= 0 || burst <= 0) {
43 WARN_ONCE(interval < 0 || burst < 0, "Negative interval (%d) or burst (%d): Uninitialized ratelimit_state structure?\n", interval, burst);
44 ret = interval == 0 || burst > 0;
45 if (!(READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED) || (!interval && !burst) ||
46 !raw_spin_trylock_irqsave(&rs->lock, flags))
47 goto nolock_ret;
48
49 /* Force re-initialization once re-enabled. */
50 rs->flags &= ~RATELIMIT_INITIALIZED;
51 goto unlock_ret;
52 }
53
54 /*
55 * If we contend on this state's lock then just check if
56 * the current burst is used or not. It might cause
57 * false positive when we are past the interval and
58 * the current lock owner is just about to reset it.
59 */
60 if (!raw_spin_trylock_irqsave(&rs->lock, flags)) {
61 if (READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED &&
62 atomic_read(v: &rs->rs_n_left) > 0 && atomic_dec_return(v: &rs->rs_n_left) >= 0)
63 ret = 1;
64 goto nolock_ret;
65 }
66
67 if (!(rs->flags & RATELIMIT_INITIALIZED)) {
68 rs->begin = jiffies;
69 rs->flags |= RATELIMIT_INITIALIZED;
70 atomic_set(v: &rs->rs_n_left, i: rs->burst);
71 }
72
73 if (time_is_before_jiffies(rs->begin + interval)) {
74 int m;
75
76 /*
77 * Reset rs_n_left ASAP to reduce false positives
78 * in parallel calls, see above.
79 */
80 atomic_set(v: &rs->rs_n_left, i: rs->burst);
81 rs->begin = jiffies;
82
83 if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
84 m = ratelimit_state_reset_miss(rs);
85 if (m) {
86 printk_deferred(KERN_WARNING
87 "%s: %d callbacks suppressed\n", func, m);
88 }
89 }
90 }
91
92 /* Note that the burst might be taken by a parallel call. */
93 if (atomic_read(v: &rs->rs_n_left) > 0 && atomic_dec_return(v: &rs->rs_n_left) >= 0)
94 ret = 1;
95
96unlock_ret:
97 raw_spin_unlock_irqrestore(&rs->lock, flags);
98
99nolock_ret:
100 if (!ret)
101 ratelimit_state_inc_miss(rs);
102
103 return ret;
104}
105EXPORT_SYMBOL(___ratelimit);
106