lib/ratelimit.c

   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 int ___ratelimit(struct ratelimit_state *rs, const char *func)
  28 {
  29         unsigned long flags;
  30         int ret;
  31
  32         if (!rs->interval)
  33                 return 1;
  34
  35         /*
  36          * If we contend on this state's lock then almost
  37          * by definition we are too busy to print a message,
  38          * in addition to the one that will be printed by
  39          * the entity that is holding the lock already:
  40          */
  41         if (!raw_spin_trylock_irqsave(&rs->lock, flags))
  42                 return 0;
  43
  44         if (!rs->begin)
  45                 rs->begin = jiffies;
  46
  47         if (time_is_before_jiffies(rs->begin + rs->interval)) {
  48                 if (rs->missed) {
  49                         if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
  50                                 printk_deferred(KERN_WARNING
  51                                                 "%s: %d callbacks suppressed\n",
  52                                                 func, rs->missed);
  53                                 rs->missed = 0;
  54                         }
  55                 }
  56                 rs->begin   = jiffies;
  57                 rs->printed = 0;
  58         }
  59         if (rs->burst && rs->burst > rs->printed) {
  60                 rs->printed++;
  61                 ret = 1;
  62         } else {
  63                 rs->missed++;
  64                 ret = 0;
  65         }
  66         raw_spin_unlock_irqrestore(&rs->lock, flags);
  67
  68         return ret;
  69 }
  70 EXPORT_SYMBOL(___ratelimit);