lib/libc/gen/nice.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  * @(#)nice.c   8.1 (Berkeley) 6/4/93
  34  * $DragonFly: src/lib/libc/gen/nice.c,v 1.3 2005/11/13 00:07:42 swildner Exp $
  35  */
  36
  37 #include <sys/types.h>
  38 #include <sys/time.h>
  39 #include <sys/resource.h>
  40 #include <errno.h>
  41 #include <unistd.h>
  42
  43 /*
  44  * Backwards compatible nice.
  45  */
  46 int
  47 nice(int incr)
  48 {
  49         int prio;
  50
  51         /*
  52          * If we aren't privileged enough to lower our nice value we shall
  53          * return EPERM, contrary to setpriority() which is required to return
  54          * EACCES.
  55          */
  56         if (incr < 0 && (geteuid() != 0)) {
  57                 errno = EPERM;
  58                 return (-1);
  59         }
  60
  61         /*
  62          * -1 is a permissible value in a successful scenario. That's why we
  63          * zero out errno and check against it afterwards, to differentiate
  64          * between a legitimate value and a failure.
  65          */
  66         errno = 0;
  67         prio = getpriority(PRIO_PROCESS, 0);
  68         if (prio == -1 && errno)
  69                 return (-1);
  70
  71         if (setpriority(PRIO_PROCESS, 0, prio + incr) == -1)
  72                 return (-1);
  73         return (getpriority(PRIO_PROCESS, 0));
  74 }