usr.bin/gprof/hertz.c

   1 /*
   2  * Copyright (c) 1983, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  *
  33  * @(#)hertz.c  8.1 (Berkeley) 6/6/93
  34  *
  35  * $DragonFly: src/usr.bin/gprof/hertz.c,v 1.3 2003/10/04 20:36:45 hmp Exp $
  36  */
  37
  38 #include <sys/time.h>
  39
  40     /*
  41      *  discover the tick frequency of the machine
  42      *  if something goes wrong, we return 0, an impossible hertz.
  43      */
  44 #define HZ_WRONG        0
  45
  46 hertz(void)
  47 {
  48         struct itimerval tim;
  49
  50         tim.it_interval.tv_sec = 0;
  51         tim.it_interval.tv_usec = 1;
  52         tim.it_value.tv_sec = 0;
  53         tim.it_value.tv_usec = 0;
  54         setitimer(ITIMER_REAL, &tim, 0);
  55         setitimer(ITIMER_REAL, 0, &tim);
  56         if (tim.it_interval.tv_usec < 2)
  57                 return(HZ_WRONG);
  58         return (1000000 / tim.it_interval.tv_usec);
  59 }