| 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); |