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 11 #include <asm/tlb.h> 12 13 #include <trace/events/power.h> 14 15 static int __read_mostly cpu_idle_force_poll; 16 17 void cpu_idle_poll_ctrl(bool enable) 18 { 19 if (enable) { 20 cpu_idle_force_poll++; 21 } else { 22 cpu_idle_force_poll--; 23 WARN_ON_ONCE(cpu_idle_force_poll < 0); 24 } 25 } 26 27 #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP 28 static int __init cpu_idle_poll_setup(char *__unused) 29 { 30 cpu_idle_force_poll = 1; 31 return 1; 32 } 33 __setup("nohlt", cpu_idle_poll_setup); 34 35 static int __init cpu_idle_nopoll_setup(char *__unused) 36 { 37 cpu_idle_force_poll = 0; 38 return 1; 39 } 40 __setup("hlt", cpu_idle_nopoll_setup); 41 #endif 42 43 static inline int cpu_idle_poll(void) 44 { 45 rcu_idle_enter(); 46 trace_cpu_idle_rcuidle(0, smp_processor_id()); 47 local_irq_enable(); 48 while (!tif_need_resched()) 49 cpu_relax(); 50 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); 51 rcu_idle_exit(); 52 return 1; 53 } 54 55 /* Weak implementations for optional arch specific functions */ 56 void __weak arch_cpu_idle_prepare(void) { } 57 void __weak arch_cpu_idle_enter(void) { } 58 void __weak arch_cpu_idle_exit(void) { } 59 void __weak arch_cpu_idle_dead(void) { } 60 void __weak arch_cpu_idle(void) 61 { 62 cpu_idle_force_poll = 1; 63 local_irq_enable(); 64 } 65 66 /** 67 * cpuidle_idle_call - the main idle function 68 * 69 * NOTE: no locks or semaphores should be used here 70 * return non-zero on failure 71 */ 72 static int cpuidle_idle_call(void) 73 { 74 struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); 75 struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); 76 int next_state, entered_state, ret; 77 bool broadcast; 78 79 /* 80 * Check if the idle task must be rescheduled. If it is the 81 * case, exit the function after re-enabling the local irq and 82 * set again the polling flag 83 */ 84 if (current_clr_polling_and_test()) { 85 local_irq_enable(); 86 __current_set_polling(); 87 return 0; 88 } 89 90 /* 91 * During the idle period, stop measuring the disabled irqs 92 * critical sections latencies 93 */ 94 stop_critical_timings(); 95 96 /* 97 * Tell the RCU framework we are entering an idle section, 98 * so no more rcu read side critical sections and one more 99 * step to the grace period 100 */ 101 rcu_idle_enter(); 102 103 /* 104 * Check if the cpuidle framework is ready, otherwise fallback 105 * to the default arch specific idle method 106 */ 107 ret = cpuidle_enabled(drv, dev); 108 109 if (!ret) { 110 /* 111 * Ask the governor to choose an idle state it thinks 112 * it is convenient to go to. There is *always* a 113 * convenient idle state 114 */ 115 next_state = cpuidle_select(drv, dev); 116 117 /* 118 * The idle task must be scheduled, it is pointless to 119 * go to idle, just update no idle residency and get 120 * out of this function 121 */ 122 if (current_clr_polling_and_test()) { 123 dev->last_residency = 0; 124 entered_state = next_state; 125 local_irq_enable(); 126 } else { 127 broadcast = !!(drv->states[next_state].flags & 128 CPUIDLE_FLAG_TIMER_STOP); 129 130 if (broadcast) 131 /* 132 * Tell the time framework to switch 133 * to a broadcast timer because our 134 * local timer will be shutdown. If a 135 * local timer is used from another 136 * cpu as a broadcast timer, this call 137 * may fail if it is not available 138 */ 139 ret = clockevents_notify( 140 CLOCK_EVT_NOTIFY_BROADCAST_ENTER, 141 &dev->cpu); 142 143 if (!ret) { 144 trace_cpu_idle_rcuidle(next_state, dev->cpu); 145 146 /* 147 * Enter the idle state previously 148 * returned by the governor 149 * decision. This function will block 150 * until an interrupt occurs and will 151 * take care of re-enabling the local 152 * interrupts 153 */ 154 entered_state = cpuidle_enter(drv, dev, 155 next_state); 156 157 trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, 158 dev->cpu); 159 160 if (broadcast) 161 clockevents_notify( 162 CLOCK_EVT_NOTIFY_BROADCAST_EXIT, 163 &dev->cpu); 164 165 /* 166 * Give the governor an opportunity to reflect on the 167 * outcome 168 */ 169 cpuidle_reflect(dev, entered_state); 170 } 171 } 172 } 173 174 /* 175 * We can't use the cpuidle framework, let's use the default 176 * idle routine 177 */ 178 if (ret) 179 arch_cpu_idle(); 180 181 __current_set_polling(); 182 183 /* 184 * It is up to the idle functions to enable back the local 185 * interrupt 186 */ 187 if (WARN_ON_ONCE(irqs_disabled())) 188 local_irq_enable(); 189 190 rcu_idle_exit(); 191 start_critical_timings(); 192 193 return 0; 194 } 195 196 /* 197 * Generic idle loop implementation 198 */ 199 static void cpu_idle_loop(void) 200 { 201 while (1) { 202 tick_nohz_idle_enter(); 203 204 while (!need_resched()) { 205 check_pgt_cache(); 206 rmb(); 207 208 if (cpu_is_offline(smp_processor_id())) 209 arch_cpu_idle_dead(); 210 211 local_irq_disable(); 212 arch_cpu_idle_enter(); 213 214 /* 215 * In poll mode we reenable interrupts and spin. 216 * 217 * Also if we detected in the wakeup from idle 218 * path that the tick broadcast device expired 219 * for us, we don't want to go deep idle as we 220 * know that the IPI is going to arrive right 221 * away 222 */ 223 if (cpu_idle_force_poll || tick_check_broadcast_expired()) 224 cpu_idle_poll(); 225 else 226 cpuidle_idle_call(); 227 228 arch_cpu_idle_exit(); 229 } 230 231 /* 232 * Since we fell out of the loop above, we know 233 * TIF_NEED_RESCHED must be set, propagate it into 234 * PREEMPT_NEED_RESCHED. 235 * 236 * This is required because for polling idle loops we will 237 * not have had an IPI to fold the state for us. 238 */ 239 preempt_set_need_resched(); 240 tick_nohz_idle_exit(); 241 schedule_preempt_disabled(); 242 } 243 } 244 245 void cpu_startup_entry(enum cpuhp_state state) 246 { 247 /* 248 * This #ifdef needs to die, but it's too late in the cycle to 249 * make this generic (arm and sh have never invoked the canary 250 * init for the non boot cpus!). Will be fixed in 3.11 251 */ 252 #ifdef CONFIG_X86 253 /* 254 * If we're the non-boot CPU, nothing set the stack canary up 255 * for us. The boot CPU already has it initialized but no harm 256 * in doing it again. This is a good place for updating it, as 257 * we wont ever return from this function (so the invalid 258 * canaries already on the stack wont ever trigger). 259 */ 260 boot_init_stack_canary(); 261 #endif 262 __current_set_polling(); 263 arch_cpu_idle_prepare(); 264 cpu_idle_loop(); 265 } 266