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      1 /*	$NetBSD: ratelimit.h,v 1.6 2022/04/09 23:44:25 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2013 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Taylor R. Campbell.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #ifndef _LINUX_RATELIMIT_H_
     33 #define _LINUX_RATELIMIT_H_
     34 
     35 #include <sys/atomic.h>
     36 #include <sys/stdbool.h>
     37 #include <sys/time.h>
     38 
     39 #define	ratelimit_state	linux_ratelimit_state
     40 
     41 struct ratelimit_state {
     42 	volatile int		missed;
     43 
     44 	volatile unsigned	rl_lock;
     45 	struct timeval		rl_lasttime;
     46 	int			rl_curpps;
     47 	unsigned		rl_maxpps;
     48 };
     49 
     50 enum {
     51 	RATELIMIT_MSG_ON_RELEASE,
     52 };
     53 
     54 /*
     55  * XXX Assumes hz=100 so this works in static initializers, and/or
     56  * hopes the caller just uses DEFAULT_RATELIMIT_INTERVAL and doesn't
     57  * mention hz.
     58  */
     59 #define	DEFAULT_RATELIMIT_INTERVAL	(5*100)
     60 #define	DEFAULT_RATELIMIT_BURST		10
     61 
     62 #define	DEFINE_RATELIMIT_STATE(n, i, b)					      \
     63 	struct ratelimit_state n = {					      \
     64 		.missed = 0,						      \
     65 		.rl_lock = 0,						      \
     66 		.rl_lasttime = { .tv_sec = 0, .tv_usec = 0 },		      \
     67 		.rl_curpps = 0,						      \
     68 		.rl_maxpps = (b)/((i)/100),				      \
     69 	}
     70 
     71 static inline void
     72 ratelimit_state_init(struct ratelimit_state *r, int interval, int burst)
     73 {
     74 
     75 	memset(r, 0, sizeof(*r));
     76 	r->rl_maxpps = burst/(interval/hz);
     77 }
     78 
     79 static inline void
     80 ratelimit_set_flags(struct ratelimit_state *r, unsigned long flags)
     81 {
     82 }
     83 
     84 static inline bool
     85 __ratelimit(struct ratelimit_state *r)
     86 {
     87 	int ok;
     88 
     89 	if (atomic_swap_uint(&r->rl_lock, 1)) {
     90 		ok = false;
     91 		goto out;
     92 	}
     93 	membar_acquire();
     94 	ok = ppsratecheck(&r->rl_lasttime, &r->rl_curpps, r->rl_maxpps);
     95 	atomic_store_release(&r->rl_lock, 0);
     96 
     97 out:	if (!ok)
     98 		atomic_store_relaxed(&r->missed, 1);
     99 	return ok;
    100 }
    101 
    102 #endif  /* _LINUX_RATELIMIT_H_ */
    103