Root/lib/ratelimit.c

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/module.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 */
28int ___ratelimit(struct ratelimit_state *rs, const char *func)
29{
30    unsigned long flags;
31    int ret;
32
33    if (!rs->interval)
34        return 1;
35
36    /*
37     * If we contend on this state's lock then almost
38     * by definition we are too busy to print a message,
39     * in addition to the one that will be printed by
40     * the entity that is holding the lock already:
41     */
42    if (!spin_trylock_irqsave(&rs->lock, flags))
43        return 0;
44
45    if (!rs->begin)
46        rs->begin = jiffies;
47
48    if (time_is_before_jiffies(rs->begin + rs->interval)) {
49        if (rs->missed)
50            printk(KERN_WARNING "%s: %d callbacks suppressed\n",
51                func, rs->missed);
52        rs->begin = 0;
53        rs->printed = 0;
54        rs->missed = 0;
55    }
56    if (rs->burst && rs->burst > rs->printed) {
57        rs->printed++;
58        ret = 1;
59    } else {
60        rs->missed++;
61        ret = 0;
62    }
63    spin_unlock_irqrestore(&rs->lock, flags);
64
65    return ret;
66}
67EXPORT_SYMBOL(___ratelimit);
68

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