1 /* $NetBSD: kern_idle.c,v 1.36 2024/03/01 04:32:38 mrg 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 1.36 2024/03/01 04:32:38 mrg 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> /* uvm_idle */
43
44 void
idle_loop(void * dummy)45 idle_loop(void *dummy)
46 {
47 struct cpu_info *ci = curcpu();
48 struct schedstate_percpu *spc;
49 struct lwp *l = curlwp;
50
51 KASSERT(l->l_blcnt == 0);
52
53 lwp_lock(l);
54 spc = &ci->ci_schedstate;
55 KASSERT(lwp_locked(l, spc->spc_lwplock));
56 kcpuset_atomic_set(kcpuset_running, cpu_index(ci));
57 /* Update start time for this thread. */
58 binuptime(&l->l_stime);
59 spc->spc_flags |= SPCF_RUNNING;
60 KASSERT((l->l_pflag & LP_RUNNING) != 0);
61 l->l_stat = LSIDL;
62 lwp_unlock(l);
63
64 /*
65 * Use spl0() here to ensure that we have the correct interrupt
66 * priority. This may be the first thread running on the CPU,
67 * in which case we took an odd route to get here.
68 */
69 spl0();
70
71 for (;;) {
72 LOCKDEBUG_BARRIER(NULL, 0);
73 KASSERT((l->l_flag & LW_IDLE) != 0);
74 KASSERT(ci == curcpu());
75 KASSERT(l == curlwp);
76 KASSERT(CURCPU_IDLE_P());
77 KASSERT(l->l_priority == PRI_IDLE);
78 KASSERTMSG(l->l_nopreempt == 0, "lwp %p nopreempt %d",
79 l, l->l_nopreempt);
80
81 sched_idle();
82 if (!sched_curcpu_runnable_p()) {
83 if ((spc->spc_flags & SPCF_OFFLINE) == 0) {
84 uvm_idle();
85 }
86 if (!sched_curcpu_runnable_p()) {
87 cpu_idle();
88 if (!sched_curcpu_runnable_p() &&
89 !ci->ci_want_resched) {
90 continue;
91 }
92 }
93 }
94 KASSERT(l->l_mutex == l->l_cpu->ci_schedstate.spc_lwplock);
95 lwp_lock(l);
96 spc_lock(l->l_cpu);
97 mi_switch(l);
98 KASSERT(curlwp == l);
99 KASSERT(l->l_stat == LSIDL);
100 }
101 }
102
103 int
create_idle_lwp(struct cpu_info * ci)104 create_idle_lwp(struct cpu_info *ci)
105 {
106 lwp_t *l;
107 int error;
108
109 KASSERT(ci->ci_data.cpu_idlelwp == NULL);
110 error = kthread_create(PRI_IDLE, KTHREAD_MPSAFE | KTHREAD_IDLE,
111 ci, idle_loop, NULL, &l, "idle/%u", ci->ci_index);
112 if (error != 0)
113 panic("create_idle_lwp: error %d", error);
114 lwp_lock(l);
115 l->l_flag |= LW_IDLE;
116 if (ci != lwp0.l_cpu) {
117 /*
118 * For secondary CPUs, the idle LWP is the first to run, and
119 * it's directly entered from MD code without a trip through
120 * mi_switch(). Make the picture look good in case the CPU
121 * takes an interrupt before it calls idle_loop().
122 */
123 l->l_stat = LSIDL;
124 l->l_pflag |= LP_RUNNING;
125 ci->ci_onproc = l;
126 }
127 lwp_unlock(l);
128 ci->ci_data.cpu_idlelwp = l;
129
130 return error;
131 }
132