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 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 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