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