kernel/syscall/yield.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, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1996-2002 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
  31 #pragma ident   "%Z%%M% %I%     %E% SMI"
  32
  33 #include <sys/param.h>
  34 #include <sys/types.h>
  35 #include <sys/sysmacros.h>
  36 #include <sys/systm.h>
  37 #include <sys/errno.h>
  38 #include <sys/thread.h>
  39 #include <sys/disp.h>
  40 #include <sys/debug.h>
  41 #include <sys/cpuvar.h>
  42
  43
  44 /*
  45  * The calling LWP is preempted in favor of some other LWP.
  46  */
  47 int
  48 yield()
  49 {
  50         kthread_t *t = curthread;
  51         klwp_t *lwp = ttolwp(t);
  52
  53         thread_lock(t);
  54         lwp->lwp_ru.nvcsw++;
  55         THREAD_TRANSITION(t);
  56         CL_YIELD(t);            /* does setbackdq */
  57         thread_unlock_nopreempt(t);
  58         swtch();                /* clears cpu_runrun and cpu_kprunrun */
  59
  60         return (0);
  61 }