kern_kthread.c revision 1.44 
1/*	$NetBSD: kern_kthread.c,v 1.44 2019/11/23 19:42:52 ad Exp $	*/
2
3/*-
4 * Copyright (c) 1998, 1999, 2007, 2009, 2019 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
9 * NASA Ames Research Center, and by Andrew Doran.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 *    notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 *    notice, this list of conditions and the following disclaimer in the
18 *    documentation and/or other materials provided with the distribution.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
22 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
23 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
24 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
25 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
26 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
30 * POSSIBILITY OF SUCH DAMAGE.
31 */
32
33#include <sys/cdefs.h>
34__KERNEL_RCSID(0, "$NetBSD: kern_kthread.c,v 1.44 2019/11/23 19:42:52 ad Exp $");
35
36#include <sys/param.h>
37#include <sys/systm.h>
38#include <sys/kernel.h>
39#include <sys/kthread.h>
40#include <sys/mutex.h>
41#include <sys/sched.h>
42#include <sys/kmem.h>
43
44#include <uvm/uvm_extern.h>
45
46static lwp_t *		kthread_jtarget;
47static kmutex_t		kthread_lock;
48static kcondvar_t	kthread_cv;
49
50void
51kthread_sysinit(void)
52{
53
54	mutex_init(&kthread_lock, MUTEX_DEFAULT, IPL_NONE);
55	cv_init(&kthread_cv, "kthrwait");
56	kthread_jtarget = NULL;
57}
58
59/*
60 * kthread_create: create a kernel thread, that is, system-only LWP.
61 */
62int
63kthread_create(pri_t pri, int flag, struct cpu_info *ci,
64    void (*func)(void *), void *arg, lwp_t **lp, const char *fmt, ...)
65{
66	lwp_t *l;
67	vaddr_t uaddr;
68	int error, lc;
69	va_list ap;
70
71	KASSERT((flag & KTHREAD_INTR) == 0 || (flag & KTHREAD_MPSAFE) != 0);
72
73	uaddr = uvm_uarea_system_alloc(
74	   (flag & (KTHREAD_INTR|KTHREAD_IDLE)) == KTHREAD_IDLE ? ci : NULL);
75	if (uaddr == 0) {
76		return ENOMEM;
77	}
78	if ((flag & KTHREAD_TS) != 0) {
79		lc = SCHED_OTHER;
80	} else {
81		lc = SCHED_RR;
82	}
83
84	error = lwp_create(&lwp0, &proc0, uaddr, LWP_DETACHED, NULL,
85	    0, func, arg, &l, lc, &lwp0.l_sigmask, &lwp0.l_sigstk);
86	if (error) {
87		uvm_uarea_system_free(uaddr);
88		return error;
89	}
90	if (fmt != NULL) {
91		l->l_name = kmem_alloc(MAXCOMLEN, KM_SLEEP);
92		va_start(ap, fmt);
93		vsnprintf(l->l_name, MAXCOMLEN, fmt, ap);
94		va_end(ap);
95	}
96
97	/*
98	 * Set parameters.
99	 */
100	if (pri == PRI_NONE) {
101		if ((flag & KTHREAD_TS) != 0) {
102			/* Maximum user priority level. */
103			pri = MAXPRI_USER;
104		} else {
105			/* Minimum kernel priority level. */
106			pri = PRI_KTHREAD;
107		}
108	}
109	mutex_enter(proc0.p_lock);
110	lwp_lock(l);
111	lwp_changepri(l, pri);
112	if (ci != NULL) {
113		if (ci != l->l_cpu) {
114			lwp_unlock_to(l, ci->ci_schedstate.spc_lwplock);
115			lwp_lock(l);
116		}
117		l->l_pflag |= LP_BOUND;
118		l->l_cpu = ci;
119	}
120
121	if ((flag & KTHREAD_MUSTJOIN) != 0) {
122		KASSERT(lp != NULL);
123		l->l_pflag |= LP_MUSTJOIN;
124	}
125	if ((flag & KTHREAD_INTR) != 0) {
126		l->l_pflag |= LP_INTR;
127	}
128	if ((flag & KTHREAD_MPSAFE) == 0) {
129		l->l_pflag &= ~LP_MPSAFE;
130	}
131
132	/*
133	 * Set the new LWP running, unless the caller has requested
134	 * otherwise.
135	 */
136	KASSERT(l->l_stat == LSIDL);
137	if ((flag & KTHREAD_IDLE) == 0) {
138		setrunnable(l);
139		/* LWP now unlocked */
140	} else {
141		lwp_unlock(l);
142	}
143	mutex_exit(proc0.p_lock);
144
145	/* All done! */
146	if (lp != NULL) {
147		*lp = l;
148	}
149	return 0;
150}
151
152/*
153 * Cause a kernel thread to exit.  Assumes the exiting thread is the
154 * current context.
155 */
156void
157kthread_exit(int ecode)
158{
159	const char *name;
160	lwp_t *l = curlwp;
161
162	/* We can't do much with the exit code, so just report it. */
163	if (ecode != 0) {
164		if ((name = l->l_name) == NULL)
165			name = "unnamed";
166		printf("WARNING: kthread `%s' (%d) exits with status %d\n",
167		    name, l->l_lid, ecode);
168	}
169
170	/* Barrier for joining. */
171	if (l->l_pflag & LP_MUSTJOIN) {
172		mutex_enter(&kthread_lock);
173		while (kthread_jtarget != l) {
174			cv_wait(&kthread_cv, &kthread_lock);
175		}
176		kthread_jtarget = NULL;
177		cv_broadcast(&kthread_cv);
178		mutex_exit(&kthread_lock);
179	}
180
181	/* And exit.. */
182	lwp_exit(l);
183	panic("kthread_exit");
184}
185
186/*
187 * Wait for a kthread to exit, as pthread_join().
188 */
189int
190kthread_join(lwp_t *l)
191{
192
193	KASSERT((l->l_flag & LW_SYSTEM) != 0);
194	KASSERT((l->l_pflag & LP_MUSTJOIN) != 0);
195
196	/*
197	 * - Wait if some other thread has occupied the target.
198	 * - Specify our kthread as a target and notify it.
199	 * - Wait for the target kthread to notify us.
200	 */
201	mutex_enter(&kthread_lock);
202	while (kthread_jtarget) {
203		cv_wait(&kthread_cv, &kthread_lock);
204	}
205	kthread_jtarget = l;
206	cv_broadcast(&kthread_cv);
207	while (kthread_jtarget == l) {
208		cv_wait(&kthread_cv, &kthread_lock);
209	}
210	mutex_exit(&kthread_lock);
211
212	return 0;
213}
214