thr_setschedparam.c revision 125968 
1/*
2 * Copyright (c) 1998 Daniel Eischen <eischen@vigrid.com>.
3 * 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 Daniel Eischen.
16 * 4. Neither the name of the author nor the names of any co-contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY DANIEL EISCHEN AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * $FreeBSD: head/lib/libthr/thread/thr_setschedparam.c 125968 2004-02-18 15:26:00Z mtm $
33 */
34#include <errno.h>
35#include <sys/param.h>
36#include <pthread.h>
37#include <stdlib.h>
38#include "thr_private.h"
39
40__weak_reference(_pthread_getschedparam, pthread_getschedparam);
41__weak_reference(_pthread_setschedparam, pthread_setschedparam);
42
43int
44_pthread_getschedparam(pthread_t pthread, int *policy,
45    struct sched_param *param)
46{
47	if (param == NULL || policy == NULL)
48		return (EINVAL);
49	if (_find_thread(pthread) == ESRCH)
50		return (ESRCH);
51	param->sched_priority = pthread->base_priority;
52	*policy = pthread->attr.sched_policy;
53	return(0);
54}
55
56int
57_pthread_setschedparam(pthread_t pthread, int policy,
58	const struct sched_param *param)
59{
60	struct pthread_mutex *mtx;
61	int old_prio;
62
63	mtx = NULL;
64	old_prio = 0;
65	if ((param == NULL) || (policy < SCHED_FIFO) || (policy > SCHED_RR))
66		return (EINVAL);
67	if ((param->sched_priority < PTHREAD_MIN_PRIORITY) ||
68	    (param->sched_priority > PTHREAD_MAX_PRIORITY))
69		return (ENOTSUP);
70	if (_find_thread(pthread) != 0)
71		return (ESRCH);
72
73	/*
74	 * If the pthread is waiting on a mutex grab it now. Doing it now
75	 * even though we do not need it immediately greatly simplifies the
76	 * LOR avoidance code.
77	 */
78	do {
79		_thread_critical_enter(pthread);
80		if (pthread->state == PS_MUTEX_WAIT) {
81			mtx = pthread->data.mutex;
82			if (_spintrylock(&mtx->lock) == EBUSY)
83				_thread_critical_exit(pthread);
84			else
85				break;
86		} else {
87			break;
88		}
89	} while (1);
90
91	PTHREAD_ASSERT(pthread->active_priority >= pthread->inherited_priority,
92	    "active priority cannot be less than inherited priority");
93	old_prio = pthread->base_priority;
94	pthread->base_priority = param->sched_priority;
95	if (param->sched_priority <= pthread->active_priority) {
96		/*
97		 * Active priority is affected only if it was the
98		 * base priority and the new base priority is lower.
99		 */
100		if (pthread->active_priority == old_prio &&
101		    pthread->active_priority != pthread->inherited_priority) {
102			pthread->active_priority = param->sched_priority;
103			readjust_priorities(pthread, mtx);
104		}
105
106	} else {
107		/*
108		 * New base priority is greater than active priority. This
109		 * only affects threads that are holding priority inheritance
110		 * mutexes this thread is waiting on and its position in the
111		 * queue.
112		 */
113		pthread->active_priority = param->sched_priority;
114		readjust_priorities(pthread, mtx);
115
116	}
117	pthread->attr.sched_policy = policy;
118	_thread_critical_exit(pthread);
119	if (mtx != NULL)
120		_SPINUNLOCK(&mtx->lock);
121	return(0);
122}
123