1 /* $NetBSD: kern_idle.c,v 1.16 2008/04/26 08:09:30 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 1.16 2008/04/26 08:09:30 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 #if MAXCPUS > 32 46 #error fix this code 47 #endif 48 49 static volatile uint32_t *idle_cpus; 50 51 void 52 idle_loop(void *dummy) 53 { 54 struct cpu_info *ci = curcpu(); 55 struct lwp *l = curlwp; 56 uint32_t mask = 1 << cpu_index(ci); 57 bool set = false; 58 int s; 59 60 /* Update start time for this thread. */ 61 lwp_lock(l); 62 binuptime(&l->l_stime); 63 lwp_unlock(l); 64 65 s = splsched(); 66 ci->ci_schedstate.spc_flags |= SPCF_RUNNING; 67 splx(s); 68 69 KERNEL_UNLOCK_ALL(l, NULL); 70 l->l_stat = LSONPROC; 71 while (1 /* CONSTCOND */) { 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 79 if (uvm.page_idle_zero) { 80 if (sched_curcpu_runnable_p()) { 81 goto schedule; 82 } 83 if (!set) { 84 set = true; 85 atomic_or_32(idle_cpus, mask); 86 } 87 uvm_pageidlezero(); 88 } 89 if (!sched_curcpu_runnable_p()) { 90 if (!set) { 91 set = true; 92 atomic_or_32(idle_cpus, mask); 93 } 94 cpu_idle(); 95 if (!sched_curcpu_runnable_p() && 96 !ci->ci_want_resched) { 97 continue; 98 } 99 } 100 schedule: 101 if (set) { 102 set = false; 103 atomic_and_32(idle_cpus, ~mask); 104 } 105 KASSERT(l->l_mutex == l->l_cpu->ci_schedstate.spc_lwplock); 106 lwp_lock(l); 107 mi_switch(l); 108 KASSERT(curlwp == l); 109 KASSERT(l->l_stat == LSONPROC); 110 } 111 } 112 113 /* 114 * Find an idle CPU and remove from the idle bitmask. The bitmask 115 * is not always accurate but is "good enough" for the purpose of finding 116 * a CPU to run a job on. 117 */ 118 struct cpu_info * 119 idle_pick(void) 120 { 121 uint32_t mask; 122 u_int index; 123 124 do { 125 if ((mask = *idle_cpus) == 0) 126 return NULL; 127 index = ffs(mask) - 1; 128 } while (atomic_cas_32(idle_cpus, mask, mask ^ (1 << index)) != mask); 129 130 return cpu_lookup_byindex(index); 131 } 132 133 int 134 create_idle_lwp(struct cpu_info *ci) 135 { 136 static bool again; 137 uintptr_t addr; 138 lwp_t *l; 139 int error; 140 141 if (!again) { 142 again = true; 143 addr = (uintptr_t)kmem_alloc(coherency_unit * 2, KM_SLEEP); 144 addr = roundup(addr, coherency_unit); 145 idle_cpus = (uint32_t *)addr; 146 } 147 148 KASSERT(ci->ci_data.cpu_idlelwp == NULL); 149 error = kthread_create(PRI_IDLE, KTHREAD_MPSAFE | KTHREAD_IDLE, 150 ci, idle_loop, NULL, &l, "idle/%u", ci->ci_index); 151 if (error != 0) 152 panic("create_idle_lwp: error %d", error); 153 lwp_lock(l); 154 l->l_flag |= LW_IDLE; 155 lwp_unlock(l); 156 l->l_cpu = ci; 157 ci->ci_data.cpu_idlelwp = l; 158 159 return error; 160 } 161