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         /* 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         int interval = READ_ONCE(rs->interval);
  34         int burst = READ_ONCE(rs->burst);
  35         unsigned long flags;
  36         int ret;
  37
  38         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         if (!raw_spin_trylock_irqsave(&rs->lock, flags))
  48                 return 0;
  49
  50         if (!rs->begin)
  51                 rs->begin = jiffies;
  52
  53         if (time_is_before_jiffies(rs->begin + interval)) {
  54                 if (rs->missed) {
  55                         if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
  56                                 printk_deferred(KERN_WARNING
  57                                                 "%s: %d callbacks suppressed\n",
  58                                                 func, rs->missed);
  59                                 rs->missed = 0;
  60                         }
  61                 }
  62                 rs->begin   = jiffies;
  63                 rs->printed = 0;
  64         }
  65         if (burst && burst > rs->printed) {
  66                 rs->printed++;
  67                 ret = 1;
  68         } else {
  69                 rs->missed++;
  70                 ret = 0;
  71         }
  72         raw_spin_unlock_irqrestore(&rs->lock, flags);
  73
  74         return ret;
  75 }
  76 EXPORT_SYMBOL(___ratelimit);