FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_counter.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * 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: releng/12.0/sys/kern/subr_counter.c 336149 2018-07-10 00:18:12Z markj $");
    
    #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)
    {
    
            return (uma_zalloc_pcpu(pcpu_zone_64, flags | M_ZERO));
    }
    
    void
    counter_u64_free(counter_u64_t c)
    {
    
            uma_zfree_pcpu(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 ((u_int)(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 ((u_int)(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;
                                   if (val <= limit)
                                           val = 0;
                           }
                           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);
   }

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