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  *
  20  * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
  21  * in every @rs->ratelimit_jiffies
  22  */
  23 int __ratelimit(struct ratelimit_state *rs)
  24 {
  25         unsigned long flags;
  26         int ret;
  27
  28         if (!rs->interval)
  29                 return 1;
  30
  31         /*
  32          * If we contend on this state's lock then almost
  33          * by definition we are too busy to print a message,
  34          * in addition to the one that will be printed by
  35          * the entity that is holding the lock already:
  36          */
  37         if (!spin_trylock_irqsave(&rs->lock, flags))
  38                 return 1;
  39
  40         if (!rs->begin)
  41                 rs->begin = jiffies;
  42
  43         if (time_is_before_jiffies(rs->begin + rs->interval)) {
  44                 if (rs->missed)
  45                         printk(KERN_WARNING "%s: %d callbacks suppressed\n",
  46                                 __func__, rs->missed);
  47                 rs->begin   = 0;
  48                 rs->printed = 0;
  49                 rs->missed  = 0;
  50         }
  51         if (rs->burst && rs->burst > rs->printed) {
  52                 rs->printed++;
  53                 ret = 1;
  54         } else {
  55                 rs->missed++;
  56                 ret = 0;
  57         }
  58         spin_unlock_irqrestore(&rs->lock, flags);
  59
  60         return ret;
  61 }
  62 EXPORT_SYMBOL(__ratelimit);