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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  * This file is released under the GPLv2.
   7  *
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/jiffies.h>
  12 #include <linux/module.h>
  13
  14 /*
  15  * __ratelimit - rate limiting
  16  * @ratelimit_jiffies: minimum time in jiffies between two callbacks
  17  * @ratelimit_burst: number of callbacks we do before ratelimiting
  18  *
  19  * This enforces a rate limit: not more than @ratelimit_burst callbacks
  20  * in every ratelimit_jiffies
  21  */
  22 int __ratelimit(int ratelimit_jiffies, int ratelimit_burst)
  23 {
  24         static DEFINE_SPINLOCK(ratelimit_lock);
  25         static unsigned toks = 10 * 5 * HZ;
  26         static unsigned long last_msg;
  27         static int missed;
  28         unsigned long flags;
  29         unsigned long now = jiffies;
  30
  31         spin_lock_irqsave(&ratelimit_lock, flags);
  32         toks += now - last_msg;
  33         last_msg = now;
  34         if (toks > (ratelimit_burst * ratelimit_jiffies))
  35                 toks = ratelimit_burst * ratelimit_jiffies;
  36         if (toks >= ratelimit_jiffies) {
  37                 int lost = missed;
  38
  39                 missed = 0;
  40                 toks -= ratelimit_jiffies;
  41                 spin_unlock_irqrestore(&ratelimit_lock, flags);
  42                 if (lost)
  43                         printk(KERN_WARNING "%s: %d messages suppressed\n",
  44                                 __func__, lost);
  45                 return 1;
  46         }
  47         missed++;
  48         spin_unlock_irqrestore(&ratelimit_lock, flags);
  49         return 0;
  50 }
  51 EXPORT_SYMBOL(__ratelimit);