1 /* 2 * Generic entry point for the idle threads 3 */ 4 #include <linux/sched.h> 5 #include <linux/cpu.h> 6 #include <linux/cpuidle.h> 7 #include <linux/tick.h> 8 #include <linux/mm.h> 9 #include <linux/stackprotector.h> 10 #include <linux/suspend.h> 11 12 #include <asm/tlb.h> 13 14 #include <trace/events/power.h> 15 16 #include "sched.h" 17 18 /** 19 * sched_idle_set_state - Record idle state for the current CPU. 20 * @idle_state: State to record. 21 */ 22 void sched_idle_set_state(struct cpuidle_state *idle_state) 23 { 24 idle_set_state(this_rq(), idle_state); 25 } 26 27 static int __read_mostly cpu_idle_force_poll; 28 29 void cpu_idle_poll_ctrl(bool enable) 30 { 31 if (enable) { 32 cpu_idle_force_poll++; 33 } else { 34 cpu_idle_force_poll--; 35 WARN_ON_ONCE(cpu_idle_force_poll < 0); 36 } 37 } 38 39 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP 40 static int __init cpu_idle_poll_setup(char *__unused) 41 { 42 cpu_idle_force_poll = 1; 43 return 1; 44 } 45 __setup("nohlt", cpu_idle_poll_setup); 46 47 static int __init cpu_idle_nopoll_setup(char *__unused) 48 { 49 cpu_idle_force_poll = 0; 50 return 1; 51 } 52 __setup("hlt", cpu_idle_nopoll_setup); 53 #endif 54 55 static inline int cpu_idle_poll(void) 56 { 57 rcu_idle_enter(); 58 trace_cpu_idle_rcuidle(0, smp_processor_id()); 59 local_irq_enable(); 60 stop_critical_timings(); 61 while (!tif_need_resched() && 62 (cpu_idle_force_poll || tick_check_broadcast_expired())) 63 cpu_relax(); 64 start_critical_timings(); 65 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); 66 rcu_idle_exit(); 67 return 1; 68 } 69 70 /* Weak implementations for optional arch specific functions */ 71 void __weak arch_cpu_idle_prepare(void) { } 72 void __weak arch_cpu_idle_enter(void) { } 73 void __weak arch_cpu_idle_exit(void) { } 74 void __weak arch_cpu_idle_dead(void) { } 75 void __weak arch_cpu_idle(void) 76 { 77 cpu_idle_force_poll = 1; 78 local_irq_enable(); 79 } 80 81 /** 82 * default_idle_call - Default CPU idle routine. 83 * 84 * To use when the cpuidle framework cannot be used. 85 */ 86 void default_idle_call(void) 87 { 88 if (current_clr_polling_and_test()) { 89 local_irq_enable(); 90 } else { 91 stop_critical_timings(); 92 arch_cpu_idle(); 93 start_critical_timings(); 94 } 95 } 96 97 static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, 98 int next_state) 99 { 100 /* 101 * The idle task must be scheduled, it is pointless to go to idle, just 102 * update no idle residency and return. 103 */ 104 if (current_clr_polling_and_test()) { 105 dev->last_residency = 0; 106 local_irq_enable(); 107 return -EBUSY; 108 } 109 110 /* 111 * Enter the idle state previously returned by the governor decision. 112 * This function will block until an interrupt occurs and will take 113 * care of re-enabling the local interrupts 114 */ 115 return cpuidle_enter(drv, dev, next_state); 116 } 117 118 /** 119 * cpuidle_idle_call - the main idle function 120 * 121 * NOTE: no locks or semaphores should be used here 122 * 123 * On archs that support TIF_POLLING_NRFLAG, is called with polling 124 * set, and it returns with polling set. If it ever stops polling, it 125 * must clear the polling bit. 126 */ 127 static void cpuidle_idle_call(void) 128 { 129 struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); 130 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); 131 int next_state, entered_state; 132 133 /* 134 * Check if the idle task must be rescheduled. If it is the 135 * case, exit the function after re-enabling the local irq. 136 */ 137 if (need_resched()) { 138 local_irq_enable(); 139 return; 140 } 141 142 /* 143 * Tell the RCU framework we are entering an idle section, 144 * so no more rcu read side critical sections and one more 145 * step to the grace period 146 */ 147 rcu_idle_enter(); 148 149 if (cpuidle_not_available(drv, dev)) { 150 default_idle_call(); 151 goto exit_idle; 152 } 153 154 /* 155 * Suspend-to-idle ("freeze") is a system state in which all user space 156 * has been frozen, all I/O devices have been suspended and the only 157 * activity happens here and in iterrupts (if any). In that case bypass 158 * the cpuidle governor and go stratight for the deepest idle state 159 * available. Possibly also suspend the local tick and the entire 160 * timekeeping to prevent timer interrupts from kicking us out of idle 161 * until a proper wakeup interrupt happens. 162 */ 163 if (idle_should_freeze()) { 164 entered_state = cpuidle_enter_freeze(drv, dev); 165 if (entered_state > 0) { 166 local_irq_enable(); 167 goto exit_idle; 168 } 169 170 next_state = cpuidle_find_deepest_state(drv, dev); 171 call_cpuidle(drv, dev, next_state); 172 } else { 173 /* 174 * Ask the cpuidle framework to choose a convenient idle state. 175 */ 176 next_state = cpuidle_select(drv, dev); 177 entered_state = call_cpuidle(drv, dev, next_state); 178 /* 179 * Give the governor an opportunity to reflect on the outcome 180 */ 181 cpuidle_reflect(dev, entered_state); 182 } 183 184 exit_idle: 185 __current_set_polling(); 186 187 /* 188 * It is up to the idle functions to reenable local interrupts 189 */ 190 if (WARN_ON_ONCE(irqs_disabled())) 191 local_irq_enable(); 192 193 rcu_idle_exit(); 194 } 195 196 DEFINE_PER_CPU(bool, cpu_dead_idle); 197 198 /* 199 * Generic idle loop implementation 200 * 201 * Called with polling cleared. 202 */ 203 static void cpu_idle_loop(void) 204 { 205 while (1) { 206 /* 207 * If the arch has a polling bit, we maintain an invariant: 208 * 209 * Our polling bit is clear if we're not scheduled (i.e. if 210 * rq->curr != rq->idle). This means that, if rq->idle has 211 * the polling bit set, then setting need_resched is 212 * guaranteed to cause the cpu to reschedule. 213 */ 214 215 __current_set_polling(); 216 quiet_vmstat(); 217 tick_nohz_idle_enter(); 218 219 while (!need_resched()) { 220 check_pgt_cache(); 221 rmb(); 222 223 if (cpu_is_offline(smp_processor_id())) { 224 rcu_cpu_notify(NULL, CPU_DYING_IDLE, 225 (void *)(long)smp_processor_id()); 226 smp_mb(); /* all activity before dead. */ 227 this_cpu_write(cpu_dead_idle, true); 228 arch_cpu_idle_dead(); 229 } 230 231 local_irq_disable(); 232 arch_cpu_idle_enter(); 233 234 /* 235 * In poll mode we reenable interrupts and spin. 236 * 237 * Also if we detected in the wakeup from idle 238 * path that the tick broadcast device expired 239 * for us, we don't want to go deep idle as we 240 * know that the IPI is going to arrive right 241 * away 242 */ 243 if (cpu_idle_force_poll || tick_check_broadcast_expired()) 244 cpu_idle_poll(); 245 else 246 cpuidle_idle_call(); 247 248 arch_cpu_idle_exit(); 249 } 250 251 /* 252 * Since we fell out of the loop above, we know 253 * TIF_NEED_RESCHED must be set, propagate it into 254 * PREEMPT_NEED_RESCHED. 255 * 256 * This is required because for polling idle loops we will 257 * not have had an IPI to fold the state for us. 258 */ 259 preempt_set_need_resched(); 260 tick_nohz_idle_exit(); 261 __current_clr_polling(); 262 263 /* 264 * We promise to call sched_ttwu_pending and reschedule 265 * if need_resched is set while polling is set. That 266 * means that clearing polling needs to be visible 267 * before doing these things. 268 */ 269 smp_mb__after_atomic(); 270 271 sched_ttwu_pending(); 272 schedule_preempt_disabled(); 273 } 274 } 275 276 void cpu_startup_entry(enum cpuhp_state state) 277 { 278 /* 279 * This #ifdef needs to die, but it's too late in the cycle to 280 * make this generic (arm and sh have never invoked the canary 281 * init for the non boot cpus!). Will be fixed in 3.11 282 */ 283 #ifdef CONFIG_X86 284 /* 285 * If we're the non-boot CPU, nothing set the stack canary up 286 * for us. The boot CPU already has it initialized but no harm 287 * in doing it again. This is a good place for updating it, as 288 * we wont ever return from this function (so the invalid 289 * canaries already on the stack wont ever trigger). 290 */ 291 boot_init_stack_canary(); 292 #endif 293 arch_cpu_idle_prepare(); 294 cpu_idle_loop(); 295 } 296