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 /* Fall back to the default arch idle method on errors. */ 101 if (next_state < 0) { 102 default_idle_call(); 103 return next_state; 104 } 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 = __this_cpu_read(cpuidle_devices); 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 ("freeze") 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 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 next_state = cpuidle_find_deepest_state(drv, dev); 177 call_cpuidle(drv, dev, next_state); 178 } else { 179 /* 180 * Ask the cpuidle framework to choose a convenient idle state. 181 */ 182 next_state = cpuidle_select(drv, dev); 183 entered_state = call_cpuidle(drv, dev, next_state); 184 /* 185 * Give the governor an opportunity to reflect on the outcome 186 */ 187 cpuidle_reflect(dev, entered_state); 188 } 189 190 exit_idle: 191 __current_set_polling(); 192 193 /* 194 * It is up to the idle functions to reenable local interrupts 195 */ 196 if (WARN_ON_ONCE(irqs_disabled())) 197 local_irq_enable(); 198 199 rcu_idle_exit(); 200 } 201 202 DEFINE_PER_CPU(bool, cpu_dead_idle); 203 204 /* 205 * Generic idle loop implementation 206 * 207 * Called with polling cleared. 208 */ 209 static void cpu_idle_loop(void) 210 { 211 while (1) { 212 /* 213 * If the arch has a polling bit, we maintain an invariant: 214 * 215 * Our polling bit is clear if we're not scheduled (i.e. if 216 * rq->curr != rq->idle). This means that, if rq->idle has 217 * the polling bit set, then setting need_resched is 218 * guaranteed to cause the cpu to reschedule. 219 */ 220 221 __current_set_polling(); 222 tick_nohz_idle_enter(); 223 224 while (!need_resched()) { 225 check_pgt_cache(); 226 rmb(); 227 228 if (cpu_is_offline(smp_processor_id())) { 229 rcu_cpu_notify(NULL, CPU_DYING_IDLE, 230 (void *)(long)smp_processor_id()); 231 smp_mb(); /* all activity before dead. */ 232 this_cpu_write(cpu_dead_idle, true); 233 arch_cpu_idle_dead(); 234 } 235 236 local_irq_disable(); 237 arch_cpu_idle_enter(); 238 239 /* 240 * In poll mode we reenable interrupts and spin. 241 * 242 * Also if we detected in the wakeup from idle 243 * path that the tick broadcast device expired 244 * for us, we don't want to go deep idle as we 245 * know that the IPI is going to arrive right 246 * away 247 */ 248 if (cpu_idle_force_poll || tick_check_broadcast_expired()) 249 cpu_idle_poll(); 250 else 251 cpuidle_idle_call(); 252 253 arch_cpu_idle_exit(); 254 } 255 256 /* 257 * Since we fell out of the loop above, we know 258 * TIF_NEED_RESCHED must be set, propagate it into 259 * PREEMPT_NEED_RESCHED. 260 * 261 * This is required because for polling idle loops we will 262 * not have had an IPI to fold the state for us. 263 */ 264 preempt_set_need_resched(); 265 tick_nohz_idle_exit(); 266 __current_clr_polling(); 267 268 /* 269 * We promise to call sched_ttwu_pending and reschedule 270 * if need_resched is set while polling is set. That 271 * means that clearing polling needs to be visible 272 * before doing these things. 273 */ 274 smp_mb__after_atomic(); 275 276 sched_ttwu_pending(); 277 schedule_preempt_disabled(); 278 } 279 } 280 281 void cpu_startup_entry(enum cpuhp_state state) 282 { 283 /* 284 * This #ifdef needs to die, but it's too late in the cycle to 285 * make this generic (arm and sh have never invoked the canary 286 * init for the non boot cpus!). Will be fixed in 3.11 287 */ 288 #ifdef CONFIG_X86 289 /* 290 * If we're the non-boot CPU, nothing set the stack canary up 291 * for us. The boot CPU already has it initialized but no harm 292 * in doing it again. This is a good place for updating it, as 293 * we wont ever return from this function (so the invalid 294 * canaries already on the stack wont ever trigger). 295 */ 296 boot_init_stack_canary(); 297 #endif 298 arch_cpu_idle_prepare(); 299 cpu_idle_loop(); 300 } 301