Line data    Source code

       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/export.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          89 : int ___ratelimit(struct ratelimit_state *rs, const char *func)
      29             : {
      30             :         unsigned long flags;
      31             :         int ret;
      32             : 
      33          89 :         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          88 :         if (!raw_spin_trylock_irqsave(&rs->lock, flags))
      43             :                 return 0;
      44             : 
      45          88 :         if (!rs->begin)
      46          27 :                 rs->begin = jiffies;
      47             : 
      48          88 :         if (time_is_before_jiffies(rs->begin + rs->interval)) {
      49          24 :                 if (rs->missed)
      50           0 :                         printk(KERN_WARNING "%s: %d callbacks suppressed\n",
      51             :                                 func, rs->missed);
      52          24 :                 rs->begin   = 0;
      53          24 :                 rs->printed = 0;
      54          24 :                 rs->missed  = 0;
      55             :         }
      56          88 :         if (rs->burst && rs->burst > rs->printed) {
      57          88 :                 rs->printed++;
      58          88 :                 ret = 1;
      59             :         } else {
      60           0 :                 rs->missed++;
      61             :                 ret = 0;
      62             :         }
      63         264 :         raw_spin_unlock_irqrestore(&rs->lock, flags);
      64             : 
      65          88 :         return ret;
      66             : }
      67             : EXPORT_SYMBOL(___ratelimit);