LXR linux/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 */
  27int ___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}
  70EXPORT_SYMBOL(___ratelimit);
  71