1 /* 2 * Generic entry point for the idle threads 3 */ 4 #include <linux/sched.h> 5 #include <linux/sched/idle.h> 6 #include <linux/cpu.h> 7 #include <linux/cpuidle.h> 8 #include <linux/cpuhotplug.h> 9 #include <linux/tick.h> 10 #include <linux/mm.h> 11 #include <linux/stackprotector.h> 12 #include <linux/suspend.h> 13 #include <linux/livepatch.h> 14 15 #include <asm/tlb.h> 16 17 #include <trace/events/power.h> 18 19 #include "sched.h" 20 21 /* Linker adds these: start and end of __cpuidle functions */ 22 extern char __cpuidle_text_start[], __cpuidle_text_end[]; 23 24 /** 25 * sched_idle_set_state - Record idle state for the current CPU. 26 * @idle_state: State to record. 27 */ 28 void sched_idle_set_state(struct cpuidle_state *idle_state) 29 { 30 idle_set_state(this_rq(), idle_state); 31 } 32 33 static int __read_mostly cpu_idle_force_poll; 34 35 void cpu_idle_poll_ctrl(bool enable) 36 { 37 if (enable) { 38 cpu_idle_force_poll++; 39 } else { 40 cpu_idle_force_poll--; 41 WARN_ON_ONCE(cpu_idle_force_poll < 0); 42 } 43 } 44 45 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP 46 static int __init cpu_idle_poll_setup(char *__unused) 47 { 48 cpu_idle_force_poll = 1; 49 return 1; 50 } 51 __setup("nohlt", cpu_idle_poll_setup); 52 53 static int __init cpu_idle_nopoll_setup(char *__unused) 54 { 55 cpu_idle_force_poll = 0; 56 return 1; 57 } 58 __setup("hlt", cpu_idle_nopoll_setup); 59 #endif 60 61 static noinline int __cpuidle cpu_idle_poll(void) 62 { 63 rcu_idle_enter(); 64 trace_cpu_idle_rcuidle(0, smp_processor_id()); 65 local_irq_enable(); 66 stop_critical_timings(); 67 while (!tif_need_resched() && 68 (cpu_idle_force_poll || tick_check_broadcast_expired())) 69 cpu_relax(); 70 start_critical_timings(); 71 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); 72 rcu_idle_exit(); 73 return 1; 74 } 75 76 /* Weak implementations for optional arch specific functions */ 77 void __weak arch_cpu_idle_prepare(void) { } 78 void __weak arch_cpu_idle_enter(void) { } 79 void __weak arch_cpu_idle_exit(void) { } 80 void __weak arch_cpu_idle_dead(void) { } 81 void __weak arch_cpu_idle(void) 82 { 83 cpu_idle_force_poll = 1; 84 local_irq_enable(); 85 } 86 87 /** 88 * default_idle_call - Default CPU idle routine. 89 * 90 * To use when the cpuidle framework cannot be used. 91 */ 92 void __cpuidle default_idle_call(void) 93 { 94 if (current_clr_polling_and_test()) { 95 local_irq_enable(); 96 } else { 97 stop_critical_timings(); 98 arch_cpu_idle(); 99 start_critical_timings(); 100 } 101 } 102 103 static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, 104 int next_state) 105 { 106 /* 107 * The idle task must be scheduled, it is pointless to go to idle, just 108 * update no idle residency and return. 109 */ 110 if (current_clr_polling_and_test()) { 111 dev->last_residency = 0; 112 local_irq_enable(); 113 return -EBUSY; 114 } 115 116 /* 117 * Enter the idle state previously returned by the governor decision. 118 * This function will block until an interrupt occurs and will take 119 * care of re-enabling the local interrupts 120 */ 121 return cpuidle_enter(drv, dev, next_state); 122 } 123 124 /** 125 * cpuidle_idle_call - the main idle function 126 * 127 * NOTE: no locks or semaphores should be used here 128 * 129 * On archs that support TIF_POLLING_NRFLAG, is called with polling 130 * set, and it returns with polling set. If it ever stops polling, it 131 * must clear the polling bit. 132 */ 133 static void cpuidle_idle_call(void) 134 { 135 struct cpuidle_device *dev = cpuidle_get_device(); 136 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); 137 int next_state, entered_state; 138 139 /* 140 * Check if the idle task must be rescheduled. If it is the 141 * case, exit the function after re-enabling the local irq. 142 */ 143 if (need_resched()) { 144 local_irq_enable(); 145 return; 146 } 147 148 /* 149 * Tell the RCU framework we are entering an idle section, 150 * so no more rcu read side critical sections and one more 151 * step to the grace period 152 */ 153 rcu_idle_enter(); 154 155 if (cpuidle_not_available(drv, dev)) { 156 default_idle_call(); 157 goto exit_idle; 158 } 159 160 /* 161 * Suspend-to-idle ("s2idle") is a system state in which all user space 162 * has been frozen, all I/O devices have been suspended and the only 163 * activity happens here and in iterrupts (if any). In that case bypass 164 * the cpuidle governor and go stratight for the deepest idle state 165 * available. Possibly also suspend the local tick and the entire 166 * timekeeping to prevent timer interrupts from kicking us out of idle 167 * until a proper wakeup interrupt happens. 168 */ 169 170 if (idle_should_enter_s2idle() || dev->use_deepest_state) { 171 if (idle_should_enter_s2idle()) { 172 entered_state = cpuidle_enter_s2idle(drv, dev); 173 if (entered_state > 0) { 174 local_irq_enable(); 175 goto exit_idle; 176 } 177 } 178 179 next_state = cpuidle_find_deepest_state(drv, dev); 180 call_cpuidle(drv, dev, next_state); 181 } else { 182 /* 183 * Ask the cpuidle framework to choose a convenient idle state. 184 */ 185 next_state = cpuidle_select(drv, dev); 186 entered_state = call_cpuidle(drv, dev, next_state); 187 /* 188 * Give the governor an opportunity to reflect on the outcome 189 */ 190 cpuidle_reflect(dev, entered_state); 191 } 192 193 exit_idle: 194 __current_set_polling(); 195 196 /* 197 * It is up to the idle functions to reenable local interrupts 198 */ 199 if (WARN_ON_ONCE(irqs_disabled())) 200 local_irq_enable(); 201 202 rcu_idle_exit(); 203 } 204 205 /* 206 * Generic idle loop implementation 207 * 208 * Called with polling cleared. 209 */ 210 static void do_idle(void) 211 { 212 int cpu = smp_processor_id(); 213 /* 214 * If the arch has a polling bit, we maintain an invariant: 215 * 216 * Our polling bit is clear if we're not scheduled (i.e. if rq->curr != 217 * rq->idle). This means that, if rq->idle has the polling bit set, 218 * then setting need_resched is guaranteed to cause the CPU to 219 * reschedule. 220 */ 221 222 __current_set_polling(); 223 tick_nohz_idle_enter(); 224 225 while (!need_resched()) { 226 check_pgt_cache(); 227 rmb(); 228 229 if (cpu_is_offline(cpu)) { 230 cpuhp_report_idle_dead(); 231 arch_cpu_idle_dead(); 232 } 233 234 local_irq_disable(); 235 arch_cpu_idle_enter(); 236 237 /* 238 * In poll mode we reenable interrupts and spin. Also if we 239 * detected in the wakeup from idle path that the tick 240 * broadcast device expired for us, we don't want to go deep 241 * idle as we know that the IPI is going to arrive right away. 242 */ 243 if (cpu_idle_force_poll || tick_check_broadcast_expired()) 244 cpu_idle_poll(); 245 else 246 cpuidle_idle_call(); 247 arch_cpu_idle_exit(); 248 } 249 250 /* 251 * Since we fell out of the loop above, we know TIF_NEED_RESCHED must 252 * be set, propagate it into PREEMPT_NEED_RESCHED. 253 * 254 * This is required because for polling idle loops we will not have had 255 * an IPI to fold the state for us. 256 */ 257 preempt_set_need_resched(); 258 tick_nohz_idle_exit(); 259 __current_clr_polling(); 260 261 /* 262 * We promise to call sched_ttwu_pending() and reschedule if 263 * need_resched() is set while polling is set. That means that clearing 264 * polling needs to be visible before doing these things. 265 */ 266 smp_mb__after_atomic(); 267 268 sched_ttwu_pending(); 269 schedule_idle(); 270 271 if (unlikely(klp_patch_pending(current))) 272 klp_update_patch_state(current); 273 } 274 275 bool cpu_in_idle(unsigned long pc) 276 { 277 return pc >= (unsigned long)__cpuidle_text_start && 278 pc < (unsigned long)__cpuidle_text_end; 279 } 280 281 struct idle_timer { 282 struct hrtimer timer; 283 int done; 284 }; 285 286 static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer) 287 { 288 struct idle_timer *it = container_of(timer, struct idle_timer, timer); 289 290 WRITE_ONCE(it->done, 1); 291 set_tsk_need_resched(current); 292 293 return HRTIMER_NORESTART; 294 } 295 296 void play_idle(unsigned long duration_ms) 297 { 298 struct idle_timer it; 299 300 /* 301 * Only FIFO tasks can disable the tick since they don't need the forced 302 * preemption. 303 */ 304 WARN_ON_ONCE(current->policy != SCHED_FIFO); 305 WARN_ON_ONCE(current->nr_cpus_allowed != 1); 306 WARN_ON_ONCE(!(current->flags & PF_KTHREAD)); 307 WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY)); 308 WARN_ON_ONCE(!duration_ms); 309 310 rcu_sleep_check(); 311 preempt_disable(); 312 current->flags |= PF_IDLE; 313 cpuidle_use_deepest_state(true); 314 315 it.done = 0; 316 hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 317 it.timer.function = idle_inject_timer_fn; 318 hrtimer_start(&it.timer, ms_to_ktime(duration_ms), HRTIMER_MODE_REL_PINNED); 319 320 while (!READ_ONCE(it.done)) 321 do_idle(); 322 323 cpuidle_use_deepest_state(false); 324 current->flags &= ~PF_IDLE; 325 326 preempt_fold_need_resched(); 327 preempt_enable(); 328 } 329 EXPORT_SYMBOL_GPL(play_idle); 330 331 void cpu_startup_entry(enum cpuhp_state state) 332 { 333 /* 334 * This #ifdef needs to die, but it's too late in the cycle to 335 * make this generic (arm and sh have never invoked the canary 336 * init for the non boot cpus!). Will be fixed in 3.11 337 */ 338 #ifdef CONFIG_X86 339 /* 340 * If we're the non-boot CPU, nothing set the stack canary up 341 * for us. The boot CPU already has it initialized but no harm 342 * in doing it again. This is a good place for updating it, as 343 * we wont ever return from this function (so the invalid 344 * canaries already on the stack wont ever trigger). 345 */ 346 boot_init_stack_canary(); 347 #endif 348 arch_cpu_idle_prepare(); 349 cpuhp_online_idle(state); 350 while (1) 351 do_idle(); 352 } 353