xref: /illumos-gate/usr/src/uts/common/syscall/yield.c (revision 2d6eb4a5)
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 #include <sys/param.h>
31 #include <sys/types.h>
32 #include <sys/sysmacros.h>
33 #include <sys/systm.h>
34 #include <sys/errno.h>
35 #include <sys/thread.h>
36 #include <sys/disp.h>
37 #include <sys/debug.h>
38 #include <sys/cpuvar.h>
39 
40 
41 /*
42  * The calling LWP is preempted in favor of some other LWP.
43  */
44 int
yield()45 yield()
46 {
47 	kthread_t *t = curthread;
48 	klwp_t *lwp = ttolwp(t);
49 
50 	thread_lock(t);
51 	lwp->lwp_ru.nvcsw++;
52 	THREAD_TRANSITION(t);
53 	CL_YIELD(t);		/* does setbackdq */
54 	thread_unlock_nopreempt(t);
55 	swtch();		/* clears cpu_runrun and cpu_kprunrun */
56 
57 	return (0);
58 }
59