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); 77