linux/lib/ratelimit.c
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   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 (!raw_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        raw_spin_unlock_irqrestore(&rs->lock, flags);
  64
  65        return ret;
  66}
  67EXPORT_SYMBOL(___ratelimit);
  68
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