| 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 | if (idle_should_freeze()) { |
| 168 | entered_state = cpuidle_enter_freeze(drv, dev); |
| 169 | if (entered_state > 0) { |
| 170 | local_irq_enable(); |
| 171 | goto exit_idle; |
| 172 | } |
| 173 | |
| 174 | next_state = cpuidle_find_deepest_state(drv, dev); |
| 175 | call_cpuidle(drv, dev, next_state); |
| 176 | } else { |
| 177 | /* |
| 178 | * Ask the cpuidle framework to choose a convenient idle state. |
| 179 | */ |
| 180 | next_state = cpuidle_select(drv, dev); |
| 181 | entered_state = call_cpuidle(drv, dev, next_state); |
| 182 | /* |
| 183 | * Give the governor an opportunity to reflect on the outcome |
| 184 | */ |
| 185 | cpuidle_reflect(dev, entered_state); |
| 186 | } |
| 187 | |
| 188 | exit_idle: |
| 189 | __current_set_polling(); |
| 190 | |
| 191 | /* |
| 192 | * It is up to the idle functions to reenable local interrupts |
| 193 | */ |
| 194 | if (WARN_ON_ONCE(irqs_disabled())) |
| 195 | local_irq_enable(); |
| 196 | |
| 197 | rcu_idle_exit(); |
| 198 | } |
| 199 | |
| 200 | /* |
| 201 | * Generic idle loop implementation |
| 202 | * |
| 203 | * Called with polling cleared. |
| 204 | */ |
| 205 | static void cpu_idle_loop(void) |
| 206 | { |
| 207 | int cpu = smp_processor_id(); |
| 208 | |
| 209 | while (1) { |
| 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 |
| 214 | * rq->curr != rq->idle). This means that, if rq->idle has |
| 215 | * the polling bit set, then setting need_resched is |
| 216 | * guaranteed to cause the cpu to reschedule. |
| 217 | */ |
| 218 | |
| 219 | __current_set_polling(); |
| 220 | quiet_vmstat(); |
| 221 | tick_nohz_idle_enter(); |
| 222 | |
| 223 | while (!need_resched()) { |
| 224 | check_pgt_cache(); |
| 225 | rmb(); |
| 226 | |
| 227 | if (cpu_is_offline(cpu)) { |
| 228 | cpuhp_report_idle_dead(); |
| 229 | arch_cpu_idle_dead(); |
| 230 | } |
| 231 | |
| 232 | local_irq_disable(); |
| 233 | arch_cpu_idle_enter(); |
| 234 | |
| 235 | /* |
| 236 | * In poll mode we reenable interrupts and spin. |
| 237 | * |
| 238 | * Also if we detected in the wakeup from idle |
| 239 | * path that the tick broadcast device expired |
| 240 | * for us, we don't want to go deep idle as we |
| 241 | * know that the IPI is going to arrive right |
| 242 | * away |
| 243 | */ |
| 244 | if (cpu_idle_force_poll || tick_check_broadcast_expired()) |
| 245 | cpu_idle_poll(); |
| 246 | else |
| 247 | cpuidle_idle_call(); |
| 248 | |
| 249 | arch_cpu_idle_exit(); |
| 250 | } |
| 251 | |
| 252 | /* |
| 253 | * Since we fell out of the loop above, we know |
| 254 | * TIF_NEED_RESCHED must be set, propagate it into |
| 255 | * PREEMPT_NEED_RESCHED. |
| 256 | * |
| 257 | * This is required because for polling idle loops we will |
| 258 | * not have had an IPI to fold the state for us. |
| 259 | */ |
| 260 | preempt_set_need_resched(); |
| 261 | tick_nohz_idle_exit(); |
| 262 | __current_clr_polling(); |
| 263 | |
| 264 | /* |
| 265 | * We promise to call sched_ttwu_pending and reschedule |
| 266 | * if need_resched is set while polling is set. That |
| 267 | * means that clearing polling needs to be visible |
| 268 | * before doing these things. |
| 269 | */ |
| 270 | smp_mb__after_atomic(); |
| 271 | |
| 272 | sched_ttwu_pending(); |
| 273 | schedule_preempt_disabled(); |
| 274 | } |
| 275 | } |
| 276 | |
| 277 | bool cpu_in_idle(unsigned long pc) |
| 278 | { |
| 279 | return pc >= (unsigned long)__cpuidle_text_start && |
| 280 | pc < (unsigned long)__cpuidle_text_end; |
| 281 | } |
| 282 | |
| 283 | void cpu_startup_entry(enum cpuhp_state state) |
| 284 | { |
| 285 | /* |
| 286 | * This #ifdef needs to die, but it's too late in the cycle to |
| 287 | * make this generic (arm and sh have never invoked the canary |
| 288 | * init for the non boot cpus!). Will be fixed in 3.11 |
| 289 | */ |
| 290 | #ifdef CONFIG_X86 |
| 291 | /* |
| 292 | * If we're the non-boot CPU, nothing set the stack canary up |
| 293 | * for us. The boot CPU already has it initialized but no harm |
| 294 | * in doing it again. This is a good place for updating it, as |
| 295 | * we wont ever return from this function (so the invalid |
| 296 | * canaries already on the stack wont ever trigger). |
| 297 | */ |
| 298 | boot_init_stack_canary(); |
| 299 | #endif |
| 300 | arch_cpu_idle_prepare(); |
| 301 | cpuhp_online_idle(state); |
| 302 | cpu_idle_loop(); |
| 303 | } |