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
  13 #include <linux/kernel.h>
  14 #include <linux/jiffies.h>
  15 #include <linux/module.h>
  16
  17 static DEFINE_SPINLOCK(ratelimit_lock);
  18
  19 /*
  20  * __ratelimit - rate limiting
  21  * @rs: ratelimit_state data
  22  *
  23  * This enforces a rate limit: not more than @rs->ratelimit_burst callbacks
  24  * in every @rs->ratelimit_jiffies
  25  */
  26 int __ratelimit(struct ratelimit_state *rs)
  27 {
  28         unsigned long flags;
  29
  30         if (!rs->interval)
  31                 return 1;
  32
  33         spin_lock_irqsave(&ratelimit_lock, flags);
  34         if (!rs->begin)
  35                 rs->begin = jiffies;
  36
  37         if (time_is_before_jiffies(rs->begin + rs->interval)) {
  38                 if (rs->missed)
  39                         printk(KERN_WARNING "%s: %d callbacks suppressed\n",
  40                                 __func__, rs->missed);
  41                 rs->begin = 0;
  42                 rs->printed = 0;
  43                 rs->missed = 0;
  44         }
  45         if (rs->burst && rs->burst > rs->printed)
  46                 goto print;
  47
  48         rs->missed++;
  49         spin_unlock_irqrestore(&ratelimit_lock, flags);
  50         return 0;
  51
  52 print:
  53         rs->printed++;
  54         spin_unlock_irqrestore(&ratelimit_lock, flags);
  55         return 1;
  56 }
  57 EXPORT_SYMBOL(__ratelimit);