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1// SPDX-License-Identifier: GPL-2.0-only2/*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 as8 * 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 limiting17 * @rs: ratelimit_state data18 * @func: name of calling function19 *20 * This enforces a rate limit: not more than @rs->burst callbacks21 * in every @rs->interval22 *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 /* Paired with WRITE_ONCE() in .proc_handler().30 * Changing two values seperately could be inconsistent31 * 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 almost43 * by definition we are too busy to print a message,44 * in addition to the one that will be printed by45 * 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_WARNING57 "%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}76EXPORT_SYMBOL(___ratelimit);77