xref: /netbsd-src/sys/kern/kern_idle.c (revision b1c86f5f087524e68db12794ee9c3e3da1ab17a0)
1 /*	$NetBSD: kern_idle.c,v 1.23 2009/07/19 10:11:55 yamt Exp $	*/
2 
3 /*-
4  * Copyright (c)2002, 2006, 2007 YAMAMOTO Takashi,
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26  * SUCH DAMAGE.
27  */
28 
29 #include <sys/cdefs.h>
30 
31 __KERNEL_RCSID(0, "$NetBSD: kern_idle.c,v 1.23 2009/07/19 10:11:55 yamt Exp $");
32 
33 #include <sys/param.h>
34 #include <sys/cpu.h>
35 #include <sys/idle.h>
36 #include <sys/kthread.h>
37 #include <sys/lockdebug.h>
38 #include <sys/kmem.h>
39 #include <sys/proc.h>
40 #include <sys/atomic.h>
41 
42 #include <uvm/uvm.h>
43 #include <uvm/uvm_extern.h>
44 
45 void
46 idle_loop(void *dummy)
47 {
48 	struct cpu_info *ci = curcpu();
49 	struct schedstate_percpu *spc;
50 	struct lwp *l = curlwp;
51 
52 	ci->ci_data.cpu_onproc = l;
53 
54 	/* Update start time for this thread. */
55 	lwp_lock(l);
56 	binuptime(&l->l_stime);
57 	lwp_unlock(l);
58 
59 	/*
60 	 * Use spl0() here to ensure that we have the correct interrupt
61 	 * priority.  This may be the first thread running on the CPU,
62 	 * in which case we took a dirtbag route to get here.
63 	 */
64 	spc = &ci->ci_schedstate;
65 	(void)splsched();
66 	spc->spc_flags |= SPCF_RUNNING;
67 	spl0();
68 
69 	KERNEL_UNLOCK_ALL(l, NULL);
70 	l->l_stat = LSONPROC;
71 	l->l_pflag |= LP_RUNNING;
72 	for (;;) {
73 		LOCKDEBUG_BARRIER(NULL, 0);
74 		KASSERT((l->l_flag & LW_IDLE) != 0);
75 		KASSERT(ci == curcpu());
76 		KASSERT(l == curlwp);
77 		KASSERT(CURCPU_IDLE_P());
78 		KASSERT(l->l_priority == PRI_IDLE);
79 
80 		sched_idle();
81 		if (!sched_curcpu_runnable_p()) {
82 			if ((spc->spc_flags & SPCF_OFFLINE) == 0) {
83 				uvm_pageidlezero();
84 			}
85 			if (!sched_curcpu_runnable_p()) {
86 				cpu_idle();
87 				if (!sched_curcpu_runnable_p() &&
88 				    !ci->ci_want_resched) {
89 					continue;
90 				}
91 			}
92 		}
93 		KASSERT(l->l_mutex == l->l_cpu->ci_schedstate.spc_lwplock);
94 		lwp_lock(l);
95 		mi_switch(l);
96 		KASSERT(curlwp == l);
97 		KASSERT(l->l_stat == LSONPROC);
98 	}
99 }
100 
101 int
102 create_idle_lwp(struct cpu_info *ci)
103 {
104 	lwp_t *l;
105 	int error;
106 
107 	KASSERT(ci->ci_data.cpu_idlelwp == NULL);
108 	error = kthread_create(PRI_IDLE, KTHREAD_MPSAFE | KTHREAD_IDLE,
109 	    ci, idle_loop, NULL, &l, "idle/%u", ci->ci_index);
110 	if (error != 0)
111 		panic("create_idle_lwp: error %d", error);
112 	lwp_lock(l);
113 	l->l_flag |= LW_IDLE;
114 	lwp_unlock(l);
115 	l->l_cpu = ci;
116 	ci->ci_data.cpu_idlelwp = l;
117 
118 	return error;
119 }
120