Branch data     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                 :          0 : int ___ratelimit(struct ratelimit_state *rs, const char *func)
      29                 :            : {
      30                 :            :         unsigned long flags;
      31                 :            :         int ret;
      32                 :            : 
      33         [ +  - ]:       1301 :         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 [ -  + ][ #  # ]:       2602 :         if (!raw_spin_trylock_irqsave(&rs->lock, flags))
                 [ +  - ]
      43                 :            :                 return 0;
      44                 :            : 
      45         [ +  + ]:       2602 :         if (!rs->begin)
      46                 :          4 :                 rs->begin = jiffies;
      47                 :            : 
      48         [ +  + ]:       1301 :         if (time_is_before_jiffies(rs->begin + rs->interval)) {
      49         [ -  + ]:          3 :                 if (rs->missed)
      50                 :          0 :                         printk(KERN_WARNING "%s: %d callbacks suppressed\n",
      51                 :            :                                 func, rs->missed);
      52                 :          3 :                 rs->begin   = 0;
      53                 :          3 :                 rs->printed = 0;
      54                 :          3 :                 rs->missed  = 0;
      55                 :            :         }
      56 [ +  - ][ +  + ]:       1301 :         if (rs->burst && rs->burst > rs->printed) {
      57                 :         17 :                 rs->printed++;
      58                 :         17 :                 ret = 1;
      59                 :            :         } else {
      60                 :       1284 :                 rs->missed++;
      61                 :            :                 ret = 0;
      62                 :            :         }
      63                 :       1301 :         raw_spin_unlock_irqrestore(&rs->lock, flags);
      64                 :            : 
      65                 :       1301 :         return ret;
      66                 :            : }
      67                 :            : EXPORT_SYMBOL(___ratelimit);