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  * @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  */
  28 int ___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 (!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         spin_unlock_irqrestore(&rs->lock, flags);
  64
  65         return ret;
  66 }
  67 EXPORT_SYMBOL(___ratelimit);