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. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)nice.c   8.1 (Berkeley) 6/4/93
  30  * $DragonFly: src/lib/libc/gen/nice.c,v 1.3 2005/11/13 00:07:42 swildner Exp $
  31  */
  32
  33 #include <sys/types.h>
  34 #include <sys/time.h>
  35 #include <sys/resource.h>
  36 #include <errno.h>
  37 #include <unistd.h>
  38
  39 /*
  40  * Backwards compatible nice.
  41  */
  42 int
  43 nice(int incr)
  44 {
  45         int prio;
  46
  47         /*
  48          * If we aren't privileged enough to lower our nice value we shall
  49          * return EPERM, contrary to setpriority() which is required to return
  50          * EACCES.
  51          */
  52         if (incr < 0 && (geteuid() != 0)) {
  53                 errno = EPERM;
  54                 return (-1);
  55         }
  56
  57         /*
  58          * -1 is a permissible value in a successful scenario. That's why we
  59          * zero out errno and check against it afterwards, to differentiate
  60          * between a legitimate value and a failure.
  61          */
  62         errno = 0;
  63         prio = getpriority(PRIO_PROCESS, 0);
  64         if (prio == -1 && errno)
  65                 return (-1);
  66
  67         if (setpriority(PRIO_PROCESS, 0, prio + incr) == -1)
  68                 return (-1);
  69         return (getpriority(PRIO_PROCESS, 0));
  70 }