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/cpuhotplug.h> 8 #include <linux/tick.h> 9 #include <linux/mm.h> 10 #include <linux/stackprotector.h> 11 #include <linux/suspend.h> 12 13 #include <asm/tlb.h> 14 15 #include <trace/events/power.h> 16 17 #include "sched.h" 18 19 /* Linker adds these: start and end of __cpuidle functions */ 20 extern char __cpuidle_text_start[], __cpuidle_text_end[]; 21 22 /** 23 * sched_idle_set_state - Record idle state for the current CPU. 24 * @idle_state: State to record. 25 */ 26 void sched_idle_set_state(struct cpuidle_state *idle_state) 27 { 28 idle_set_state(this_rq(), idle_state); 29 } 30 31 static int __read_mostly cpu_idle_force_poll; 32 33 void cpu_idle_poll_ctrl(bool enable) 34 { 35 if (enable) { 36 cpu_idle_force_poll++; 37 } else { 38 cpu_idle_force_poll--; 39 WARN_ON_ONCE(cpu_idle_force_poll < 0); 40 } 41 } 42 43 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP 44 static int __init cpu_idle_poll_setup(char *__unused) 45 { 46 cpu_idle_force_poll = 1; 47 return 1; 48 } 49 __setup("nohlt", cpu_idle_poll_setup); 50 51 static int __init cpu_idle_nopoll_setup(char *__unused) 52 { 53 cpu_idle_force_poll = 0; 54 return 1; 55 } 56 __setup("hlt", cpu_idle_nopoll_setup); 57 #endif 58 59 static noinline int __cpuidle cpu_idle_poll(void) 60 { 61 rcu_idle_enter(); 62 trace_cpu_idle_rcuidle(0, smp_processor_id()); 63 local_irq_enable(); 64 stop_critical_timings(); 65 while (!tif_need_resched() && 66 (cpu_idle_force_poll || tick_check_broadcast_expired())) 67 cpu_relax(); 68 start_critical_timings(); 69 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); 70 rcu_idle_exit(); 71 return 1; 72 } 73 74 /* Weak implementations for optional arch specific functions */ 75 void __weak arch_cpu_idle_prepare(void) { } 76 void __weak arch_cpu_idle_enter(void) { } 77 void __weak arch_cpu_idle_exit(void) { } 78 void __weak arch_cpu_idle_dead(void) { } 79 void __weak arch_cpu_idle(void) 80 { 81 cpu_idle_force_poll = 1; 82 local_irq_enable(); 83 } 84 85 /** 86 * default_idle_call - Default CPU idle routine. 87 * 88 * To use when the cpuidle framework cannot be used. 89 */ 90 void __cpuidle default_idle_call(void) 91 { 92 if (current_clr_polling_and_test()) { 93 local_irq_enable(); 94 } else { 95 stop_critical_timings(); 96 arch_cpu_idle(); 97 start_critical_timings(); 98 } 99 } 100 101 static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, 102 int next_state) 103 { 104 /* 105 * The idle task must be scheduled, it is pointless to go to idle, just 106 * update no idle residency and return. 107 */ 108 if (current_clr_polling_and_test()) { 109 dev->last_residency = 0; 110 local_irq_enable(); 111 return -EBUSY; 112 } 113 114 /* 115 * Enter the idle state previously returned by the governor decision. 116 * This function will block until an interrupt occurs and will take 117 * care of re-enabling the local interrupts 118 */ 119 return cpuidle_enter(drv, dev, next_state); 120 } 121 122 /** 123 * cpuidle_idle_call - the main idle function 124 * 125 * NOTE: no locks or semaphores should be used here 126 * 127 * On archs that support TIF_POLLING_NRFLAG, is called with polling 128 * set, and it returns with polling set. If it ever stops polling, it 129 * must clear the polling bit. 130 */ 131 static void cpuidle_idle_call(void) 132 { 133 struct cpuidle_device *dev = cpuidle_get_device(); 134 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); 135 int next_state, entered_state; 136 137 /* 138 * Check if the idle task must be rescheduled. If it is the 139 * case, exit the function after re-enabling the local irq. 140 */ 141 if (need_resched()) { 142 local_irq_enable(); 143 return; 144 } 145 146 /* 147 * Tell the RCU framework we are entering an idle section, 148 * so no more rcu read side critical sections and one more 149 * step to the grace period 150 */ 151 rcu_idle_enter(); 152 153 if (cpuidle_not_available(drv, dev)) { 154 default_idle_call(); 155 goto exit_idle; 156 } 157 158 /* 159 * Suspend-to-idle ("freeze") is a system state in which all user space 160 * has been frozen, all I/O devices have been suspended and the only 161 * activity happens here and in iterrupts (if any). In that case bypass 162 * the cpuidle governor and go stratight for the deepest idle state 163 * available. Possibly also suspend the local tick and the entire 164 * timekeeping to prevent timer interrupts from kicking us out of idle 165 * until a proper wakeup interrupt happens. 166 */ 167 168 if (idle_should_freeze() || dev->use_deepest_state) { 169 if (idle_should_freeze()) { 170 entered_state = cpuidle_enter_freeze(drv, dev); 171 if (entered_state > 0) { 172 local_irq_enable(); 173 goto exit_idle; 174 } 175 } 176 177 next_state = cpuidle_find_deepest_state(drv, dev); 178 call_cpuidle(drv, dev, next_state); 179 } else { 180 /* 181 * Ask the cpuidle framework to choose a convenient idle state. 182 */ 183 next_state = cpuidle_select(drv, dev); 184 entered_state = call_cpuidle(drv, dev, next_state); 185 /* 186 * Give the governor an opportunity to reflect on the outcome 187 */ 188 cpuidle_reflect(dev, entered_state); 189 } 190 191 exit_idle: 192 __current_set_polling(); 193 194 /* 195 * It is up to the idle functions to reenable local interrupts 196 */ 197 if (WARN_ON_ONCE(irqs_disabled())) 198 local_irq_enable(); 199 200 rcu_idle_exit(); 201 } 202 203 /* 204 * Generic idle loop implementation 205 * 206 * Called with polling cleared. 207 */ 208 static void do_idle(void) 209 { 210 /* 211 * If the arch has a polling bit, we maintain an invariant: 212 * 213 * Our polling bit is clear if we're not scheduled (i.e. if rq->curr != 214 * rq->idle). This means that, if rq->idle has the polling bit set, 215 * then setting need_resched is guaranteed to cause the CPU to 216 * reschedule. 217 */ 218 219 __current_set_polling(); 220 tick_nohz_idle_enter(); 221 222 while (!need_resched()) { 223 check_pgt_cache(); 224 rmb(); 225 226 if (cpu_is_offline(smp_processor_id())) { 227 cpuhp_report_idle_dead(); 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. Also if we 236 * detected in the wakeup from idle path that the tick 237 * broadcast device expired for us, we don't want to go deep 238 * idle as we know that the IPI is going to arrive right away. 239 */ 240 if (cpu_idle_force_poll || tick_check_broadcast_expired()) 241 cpu_idle_poll(); 242 else 243 cpuidle_idle_call(); 244 arch_cpu_idle_exit(); 245 } 246 247 /* 248 * Since we fell out of the loop above, we know TIF_NEED_RESCHED must 249 * be set, propagate it into PREEMPT_NEED_RESCHED. 250 * 251 * This is required because for polling idle loops we will not have had 252 * an IPI to fold the state for us. 253 */ 254 preempt_set_need_resched(); 255 tick_nohz_idle_exit(); 256 __current_clr_polling(); 257 258 /* 259 * We promise to call sched_ttwu_pending() and reschedule if 260 * need_resched() is set while polling is set. That means that clearing 261 * polling needs to be visible before doing these things. 262 */ 263 smp_mb__after_atomic(); 264 265 sched_ttwu_pending(); 266 schedule_preempt_disabled(); 267 } 268 269 bool cpu_in_idle(unsigned long pc) 270 { 271 return pc >= (unsigned long)__cpuidle_text_start && 272 pc < (unsigned long)__cpuidle_text_end; 273 } 274 275 struct idle_timer { 276 struct hrtimer timer; 277 int done; 278 }; 279 280 static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer) 281 { 282 struct idle_timer *it = container_of(timer, struct idle_timer, timer); 283 284 WRITE_ONCE(it->done, 1); 285 set_tsk_need_resched(current); 286 287 return HRTIMER_NORESTART; 288 } 289 290 void play_idle(unsigned long duration_ms) 291 { 292 struct idle_timer it; 293 294 /* 295 * Only FIFO tasks can disable the tick since they don't need the forced 296 * preemption. 297 */ 298 WARN_ON_ONCE(current->policy != SCHED_FIFO); 299 WARN_ON_ONCE(current->nr_cpus_allowed != 1); 300 WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); 301 WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY)); 302 WARN_ON_ONCE(!duration_ms); 303 304 rcu_sleep_check(); 305 preempt_disable(); 306 current->flags |= PF_IDLE; 307 cpuidle_use_deepest_state(true); 308 309 it.done = 0; 310 hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 311 it.timer.function = idle_inject_timer_fn; 312 hrtimer_start(&it.timer, ms_to_ktime(duration_ms), HRTIMER_MODE_REL_PINNED); 313 314 while (!READ_ONCE(it.done)) 315 do_idle(); 316 317 cpuidle_use_deepest_state(false); 318 current->flags &= ~PF_IDLE; 319 320 preempt_fold_need_resched(); 321 preempt_enable(); 322 } 323 EXPORT_SYMBOL_GPL(play_idle); 324 325 void cpu_startup_entry(enum cpuhp_state state) 326 { 327 /* 328 * This #ifdef needs to die, but it's too late in the cycle to 329 * make this generic (arm and sh have never invoked the canary 330 * init for the non boot cpus!). Will be fixed in 3.11 331 */ 332 #ifdef CONFIG_X86 333 /* 334 * If we're the non-boot CPU, nothing set the stack canary up 335 * for us. The boot CPU already has it initialized but no harm 336 * in doing it again. This is a good place for updating it, as 337 * we wont ever return from this function (so the invalid 338 * canaries already on the stack wont ever trigger). 339 */ 340 boot_init_stack_canary(); 341 #endif 342 arch_cpu_idle_prepare(); 343 cpuhp_online_idle(state); 344 while (1) 345 do_idle(); 346 } 347