freebsd-skq/sys/kern/subr_counter.c

/*-
 * Copyright (c) 2012 Gleb Smirnoff <glebius@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <vm/uma.h>

#define IN_SUBR_COUNTER_C
#include <sys/counter.h>
 
void
counter_u64_zero(counter_u64_t c)
{

	counter_u64_zero_inline(c);
}

uint64_t
counter_u64_fetch(counter_u64_t c)
{

	return (counter_u64_fetch_inline(c));
}

counter_u64_t
counter_u64_alloc(int flags)
{
	counter_u64_t r;

	r = uma_zalloc(pcpu_zone_64, flags);
	if (r != NULL)
		counter_u64_zero(r);

	return (r);
}

void
counter_u64_free(counter_u64_t c)
{

	uma_zfree(pcpu_zone_64, c);
}

int
sysctl_handle_counter_u64(SYSCTL_HANDLER_ARGS)
{
	uint64_t out;
	int error;

	out = counter_u64_fetch(*(counter_u64_t *)arg1);

	error = SYSCTL_OUT(req, &out, sizeof(uint64_t));

	if (error || !req->newptr)
		return (error);

	/*
	 * Any write attempt to a counter zeroes it.
	 */
	counter_u64_zero(*(counter_u64_t *)arg1);

	return (0);
}

int
sysctl_handle_counter_u64_array(SYSCTL_HANDLER_ARGS)
{
	uint64_t *out;
	int error;

	out = malloc(arg2 * sizeof(uint64_t), M_TEMP, M_WAITOK);
	for (int i = 0; i < arg2; i++)
		out[i] = counter_u64_fetch(((counter_u64_t *)arg1)[i]);

	error = SYSCTL_OUT(req, out, arg2 * sizeof(uint64_t));
	free(out, M_TEMP);

	if (error || !req->newptr)
		return (error);

	/*
	 * Any write attempt to a counter zeroes it.
	 */
	for (int i = 0; i < arg2; i++)
		counter_u64_zero(((counter_u64_t *)arg1)[i]);
 
	return (0);
}

/*
 * MP-friendly version of ppsratecheck().
 *
 * Returns non-negative if we are in the rate, negative otherwise.
 *  0 - rate limit not reached.
 * -1 - rate limit reached.
 * >0 - rate limit was reached before, and was just reset. The return value
 *      is number of events since last reset.
 */
int64_t
counter_ratecheck(struct counter_rate *cr, int64_t limit)
{
	int64_t val;
	int now;

	val = cr->cr_over;
	now = ticks;

	if (now - cr->cr_ticks >= hz) {
		/*
		 * Time to clear the structure, we are in the next second.
		 * First try unlocked read, and then proceed with atomic.
		 */
		if ((cr->cr_lock == 0) &&
		    atomic_cmpset_acq_int(&cr->cr_lock, 0, 1)) {
			/*
			 * Check if other thread has just went through the
			 * reset sequence before us.
			 */
			if (now - cr->cr_ticks >= hz) {
				val = counter_u64_fetch(cr->cr_rate);
				counter_u64_zero(cr->cr_rate);
				cr->cr_over = 0;
				cr->cr_ticks = now;
			}
			atomic_store_rel_int(&cr->cr_lock, 0);
		} else
			/*
			 * We failed to lock, in this case other thread may
			 * be running counter_u64_zero(), so it is not safe
			 * to do an update, we skip it.
			 */
			return (val);
	}

	counter_u64_add(cr->cr_rate, 1);
	if (cr->cr_over != 0)
		return (-1);
	if (counter_u64_fetch(cr->cr_rate) > limit)
		val = cr->cr_over = -1;

	return (val);
}