kernel/syscall/nice.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"        /* from SVr4.0 1.15 */
  31
  32 #include <sys/types.h>
  33 #include <sys/param.h>
  34 #include <sys/sysmacros.h>
  35 #include <sys/systm.h>
  36 #include <sys/errno.h>
  37 #include <sys/cred.h>
  38 #include <sys/proc.h>
  39 #include <sys/debug.h>
  40 #include <sys/class.h>
  41 #include <sys/mutex.h>
  42 #include <sys/schedctl.h>
  43
  44 /*
  45  * We support the nice system call for compatibility although
  46  * the priocntl system call supports a superset of nice's functionality.
  47  * We support nice only for time sharing threads.  It will fail
  48  * if called by a thread from another class.
  49  */
  50
  51 int
  52 nice(int niceness)
  53 {
  54         int error = 0;
  55         int err, retval;
  56         kthread_t *t;
  57         proc_t *p = curproc;
  58
  59         mutex_enter(&p->p_lock);
  60         t = p->p_tlist;
  61         do {
  62                 err = CL_DONICE(t, CRED(), niceness, &retval);
  63                 schedctl_set_cidpri(t);
  64                 if (error == 0 && err)
  65                         error = set_errno(err);
  66         } while ((t = t->t_forw) != p->p_tlist);
  67         mutex_exit(&p->p_lock);
  68         if (error)
  69                 return (error);
  70         return (retval);
  71 }