Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0-only
       2             : /*
       3             :  * ratelimit.c - Do something with rate limit.
       4             :  *
       5             :  * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
       6             :  *
       7             :  * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
       8             :  * parameter. Now every user can use their own standalone ratelimit_state.
       9             :  */
      10             : 
      11             : #include <linux/ratelimit.h>
      12             : #include <linux/jiffies.h>
      13             : #include <linux/export.h>
      14             : 
      15             : /*
      16             :  * __ratelimit - rate limiting
      17             :  * @rs: ratelimit_state data
      18             :  * @func: name of calling function
      19             :  *
      20             :  * This enforces a rate limit: not more than @rs->burst callbacks
      21             :  * in every @rs->interval
      22             :  *
      23             :  * RETURNS:
      24             :  * 0 means callbacks will be suppressed.
      25             :  * 1 means go ahead and do it.
      26             :  */
      27           0 : int ___ratelimit(struct ratelimit_state *rs, const char *func)
      28             : {
      29             :         /* Paired with WRITE_ONCE() in .proc_handler().
      30             :          * Changing two values seperately could be inconsistent
      31             :          * and some message could be lost.  (See: net_ratelimit_state).
      32             :          */
      33           0 :         int interval = READ_ONCE(rs->interval);
      34           0 :         int burst = READ_ONCE(rs->burst);
      35             :         unsigned long flags;
      36             :         int ret;
      37             : 
      38           0 :         if (!interval)
      39             :                 return 1;
      40             : 
      41             :         /*
      42             :          * If we contend on this state's lock then almost
      43             :          * by definition we are too busy to print a message,
      44             :          * in addition to the one that will be printed by
      45             :          * the entity that is holding the lock already:
      46             :          */
      47           0 :         if (!raw_spin_trylock_irqsave(&rs->lock, flags))
      48             :                 return 0;
      49             : 
      50           0 :         if (!rs->begin)
      51           0 :                 rs->begin = jiffies;
      52             : 
      53           0 :         if (time_is_before_jiffies(rs->begin + interval)) {
      54           0 :                 if (rs->missed) {
      55           0 :                         if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
      56           0 :                                 printk_deferred(KERN_WARNING
      57             :                                                 "%s: %d callbacks suppressed\n",
      58             :                                                 func, rs->missed);
      59           0 :                                 rs->missed = 0;
      60             :                         }
      61             :                 }
      62           0 :                 rs->begin   = jiffies;
      63           0 :                 rs->printed = 0;
      64             :         }
      65           0 :         if (burst && burst > rs->printed) {
      66           0 :                 rs->printed++;
      67           0 :                 ret = 1;
      68             :         } else {
      69           0 :                 rs->missed++;
      70           0 :                 ret = 0;
      71             :         }
      72           0 :         raw_spin_unlock_irqrestore(&rs->lock, flags);
      73             : 
      74           0 :         return ret;
      75             : }
      76             : EXPORT_SYMBOL(___ratelimit);