1 /* 2 * ratelimit.c - Do something with rate limit. 3 * 4 * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com> 5 * 6 * 2008-05-01 rewrite the function and use a ratelimit_state data struct as 7 * parameter. Now every user can use their own standalone ratelimit_state. 8 * 9 * This file is released under the GPLv2. 10 */ 11 12 #include <linux/ratelimit.h> 13 #include <linux/jiffies.h> 14 #include <linux/export.h> 15 16 /* 17 * __ratelimit - rate limiting 18 * @rs: ratelimit_state data 19 * @func: name of calling function 20 * 21 * This enforces a rate limit: not more than @rs->burst callbacks 22 * in every @rs->interval 23 * 24 * RETURNS: 25 * 0 means callbacks will be suppressed. 26 * 1 means go ahead and do it. 27 */ 28 int ___ratelimit(struct ratelimit_state *rs, const char *func) 29 { 30 unsigned long flags; 31 int ret; 32 33 if (!rs->interval) 34 return 1; 35 36 /* 37 * If we contend on this state's lock then almost 38 * by definition we are too busy to print a message, 39 * in addition to the one that will be printed by 40 * the entity that is holding the lock already: 41 */ 42 if (!raw_spin_trylock_irqsave(&rs->lock, flags)) 43 return 0; 44 45 if (!rs->begin) 46 rs->begin = jiffies; 47 48 if (time_is_before_jiffies(rs->begin + rs->interval)) { 49 if (rs->missed) 50 printk(KERN_WARNING "%s: %d callbacks suppressed\n", 51 func, rs->missed); 52 rs->begin = jiffies; 53 rs->printed = 0; 54 rs->missed = 0; 55 } 56 if (rs->burst && rs->burst > rs->printed) { 57 rs->printed++; 58 ret = 1; 59 } else { 60 rs->missed++; 61 ret = 0; 62 } 63 raw_spin_unlock_irqrestore(&rs->lock, flags); 64 65 return ret; 66 } 67 EXPORT_SYMBOL(___ratelimit); 68