| 1 | // SPDX-License-Identifier: GPL-2.0-only |
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| 2 | /* |
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| 3 | * ratelimit.c - Do something with rate limit. |
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| 4 | * |
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| 5 | * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com> |
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| 6 | * |
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| 7 | * 2008-05-01 rewrite the function and use a ratelimit_state data struct as |
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| 8 | * parameter. Now every user can use their own standalone ratelimit_state. |
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| 9 | */ |
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| 10 | |
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| 11 | #include <linux/ratelimit.h> |
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| 12 | #include <linux/jiffies.h> |
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| 13 | #include <linux/export.h> |
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| 14 | |
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| 15 | /* |
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| 16 | * __ratelimit - rate limiting |
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| 17 | * @rs: ratelimit_state data |
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| 18 | * @func: name of calling function |
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| 19 | * |
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| 20 | * This enforces a rate limit: not more than @rs->burst callbacks |
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| 21 | * in every @rs->interval |
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| 22 | * |
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| 23 | * RETURNS: |
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| 24 | * 0 means callbacks will be suppressed. |
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| 25 | * 1 means go ahead and do it. |
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| 26 | */ |
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| 27 | int ___ratelimit(struct ratelimit_state *rs, const char *func) |
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| 28 | { |
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| 29 | /* Paired with WRITE_ONCE() in .proc_handler(). |
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| 30 | * Changing two values seperately could be inconsistent |
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| 31 | * and some message could be lost. (See: net_ratelimit_state). |
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| 32 | */ |
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| 33 | int interval = READ_ONCE(rs->interval); |
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| 34 | int burst = READ_ONCE(rs->burst); |
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| 35 | unsigned long flags; |
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| 36 | int ret; |
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| 37 | |
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| 38 | if (!interval) |
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| 39 | return 1; |
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| 40 | |
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| 41 | /* |
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| 42 | * If we contend on this state's lock then almost |
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| 43 | * by definition we are too busy to print a message, |
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| 44 | * in addition to the one that will be printed by |
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| 45 | * the entity that is holding the lock already: |
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| 46 | */ |
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| 47 | if (!raw_spin_trylock_irqsave(&rs->lock, flags)) |
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| 48 | return 0; |
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| 49 | |
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| 50 | if (!rs->begin) |
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| 51 | rs->begin = jiffies; |
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| 52 | |
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| 53 | if (time_is_before_jiffies(rs->begin + interval)) { |
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| 54 | if (rs->missed) { |
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| 55 | if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) { |
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| 56 | printk_deferred(KERN_WARNING |
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| 57 | "%s: %d callbacks suppressed\n" , |
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| 58 | func, rs->missed); |
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| 59 | rs->missed = 0; |
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| 60 | } |
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| 61 | } |
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| 62 | rs->begin = jiffies; |
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| 63 | rs->printed = 0; |
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| 64 | } |
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| 65 | if (burst && burst > rs->printed) { |
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| 66 | rs->printed++; |
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| 67 | ret = 1; |
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| 68 | } else { |
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| 69 | rs->missed++; |
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| 70 | ret = 0; |
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| 71 | } |
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| 72 | raw_spin_unlock_irqrestore(&rs->lock, flags); |
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| 73 | |
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| 74 | return ret; |
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| 75 | } |
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| 76 | EXPORT_SYMBOL(___ratelimit); |
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| 77 | |
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