| /* |
| * Generic entry point for the idle threads |
| */ |
| #include <linux/sched.h> |
| #include <linux/cpu.h> |
| #include <linux/cpuidle.h> |
| #include <linux/tick.h> |
| #include <linux/mm.h> |
| #include <linux/stackprotector.h> |
| #include <linux/suspend.h> |
| |
| #include <asm/tlb.h> |
| |
| #include <trace/events/power.h> |
| |
| #include "sched.h" |
| |
| /** |
| * sched_idle_set_state - Record idle state for the current CPU. |
| * @idle_state: State to record. |
| */ |
| void sched_idle_set_state(struct cpuidle_state *idle_state, int index) |
| { |
| idle_set_state(this_rq(), idle_state); |
| idle_set_state_idx(this_rq(), index); |
| } |
| |
| static int __read_mostly cpu_idle_force_poll; |
| |
| void cpu_idle_poll_ctrl(bool enable) |
| { |
| if (enable) { |
| cpu_idle_force_poll++; |
| } else { |
| cpu_idle_force_poll--; |
| WARN_ON_ONCE(cpu_idle_force_poll < 0); |
| } |
| } |
| |
| #ifdef CONFIG_GENERIC_IDLE_POLL_SETUP |
| static int __init cpu_idle_poll_setup(char *__unused) |
| { |
| cpu_idle_force_poll = 1; |
| return 1; |
| } |
| __setup("nohlt", cpu_idle_poll_setup); |
| |
| static int __init cpu_idle_nopoll_setup(char *__unused) |
| { |
| cpu_idle_force_poll = 0; |
| return 1; |
| } |
| __setup("hlt", cpu_idle_nopoll_setup); |
| #endif |
| |
| static inline int cpu_idle_poll(void) |
| { |
| rcu_idle_enter(); |
| trace_cpu_idle_rcuidle(0, smp_processor_id()); |
| local_irq_enable(); |
| stop_critical_timings(); |
| while (!tif_need_resched() && |
| (cpu_idle_force_poll || tick_check_broadcast_expired())) |
| cpu_relax(); |
| start_critical_timings(); |
| trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); |
| rcu_idle_exit(); |
| return 1; |
| } |
| |
| /* Weak implementations for optional arch specific functions */ |
| void __weak arch_cpu_idle_prepare(void) { } |
| void __weak arch_cpu_idle_enter(void) { } |
| void __weak arch_cpu_idle_exit(void) { } |
| void __weak arch_cpu_idle_dead(void) { } |
| void __weak arch_cpu_idle(void) |
| { |
| cpu_idle_force_poll = 1; |
| local_irq_enable(); |
| } |
| |
| /** |
| * default_idle_call - Default CPU idle routine. |
| * |
| * To use when the cpuidle framework cannot be used. |
| */ |
| void default_idle_call(void) |
| { |
| if (current_clr_polling_and_test()) { |
| local_irq_enable(); |
| } else { |
| stop_critical_timings(); |
| arch_cpu_idle(); |
| start_critical_timings(); |
| } |
| } |
| |
| static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev, |
| int next_state) |
| { |
| /* Fall back to the default arch idle method on errors. */ |
| if (next_state < 0) { |
| default_idle_call(); |
| return next_state; |
| } |
| |
| /* |
| * The idle task must be scheduled, it is pointless to go to idle, just |
| * update no idle residency and return. |
| */ |
| if (current_clr_polling_and_test()) { |
| dev->last_residency = 0; |
| local_irq_enable(); |
| return -EBUSY; |
| } |
| |
| /* |
| * Enter the idle state previously returned by the governor decision. |
| * This function will block until an interrupt occurs and will take |
| * care of re-enabling the local interrupts |
| */ |
| return cpuidle_enter(drv, dev, next_state); |
| } |
| |
| /** |
| * cpuidle_idle_call - the main idle function |
| * |
| * NOTE: no locks or semaphores should be used here |
| * |
| * On archs that support TIF_POLLING_NRFLAG, is called with polling |
| * set, and it returns with polling set. If it ever stops polling, it |
| * must clear the polling bit. |
| */ |
| static void cpuidle_idle_call(void) |
| { |
| struct cpuidle_device *dev = cpuidle_get_device(); |
| struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); |
| int next_state, entered_state; |
| |
| /* |
| * Check if the idle task must be rescheduled. If it is the |
| * case, exit the function after re-enabling the local irq. |
| */ |
| if (need_resched()) { |
| local_irq_enable(); |
| return; |
| } |
| |
| /* |
| * Tell the RCU framework we are entering an idle section, |
| * so no more rcu read side critical sections and one more |
| * step to the grace period |
| */ |
| rcu_idle_enter(); |
| |
| if (cpuidle_not_available(drv, dev)) { |
| default_idle_call(); |
| goto exit_idle; |
| } |
| |
| /* |
| * Suspend-to-idle ("freeze") is a system state in which all user space |
| * has been frozen, all I/O devices have been suspended and the only |
| * activity happens here and in iterrupts (if any). In that case bypass |
| * the cpuidle governor and go stratight for the deepest idle state |
| * available. Possibly also suspend the local tick and the entire |
| * timekeeping to prevent timer interrupts from kicking us out of idle |
| * until a proper wakeup interrupt happens. |
| */ |
| if (idle_should_freeze()) { |
| entered_state = cpuidle_enter_freeze(drv, dev); |
| if (entered_state >= 0) { |
| local_irq_enable(); |
| goto exit_idle; |
| } |
| |
| next_state = cpuidle_find_deepest_state(drv, dev); |
| call_cpuidle(drv, dev, next_state); |
| } else { |
| /* |
| * Ask the cpuidle framework to choose a convenient idle state. |
| */ |
| next_state = cpuidle_select(drv, dev); |
| entered_state = call_cpuidle(drv, dev, next_state); |
| /* |
| * Give the governor an opportunity to reflect on the outcome |
| */ |
| cpuidle_reflect(dev, entered_state); |
| } |
| |
| exit_idle: |
| __current_set_polling(); |
| |
| /* |
| * It is up to the idle functions to reenable local interrupts |
| */ |
| if (WARN_ON_ONCE(irqs_disabled())) |
| local_irq_enable(); |
| |
| rcu_idle_exit(); |
| } |
| |
| DEFINE_PER_CPU(bool, cpu_dead_idle); |
| |
| /* |
| * Generic idle loop implementation |
| * |
| * Called with polling cleared. |
| */ |
| static void cpu_idle_loop(void) |
| { |
| while (1) { |
| /* |
| * If the arch has a polling bit, we maintain an invariant: |
| * |
| * Our polling bit is clear if we're not scheduled (i.e. if |
| * rq->curr != rq->idle). This means that, if rq->idle has |
| * the polling bit set, then setting need_resched is |
| * guaranteed to cause the cpu to reschedule. |
| */ |
| |
| __current_set_polling(); |
| quiet_vmstat(); |
| tick_nohz_idle_enter(); |
| |
| while (!need_resched()) { |
| check_pgt_cache(); |
| rmb(); |
| |
| if (cpu_is_offline(smp_processor_id())) { |
| rcu_cpu_notify(NULL, CPU_DYING_IDLE, |
| (void *)(long)smp_processor_id()); |
| smp_mb(); /* all activity before dead. */ |
| this_cpu_write(cpu_dead_idle, true); |
| arch_cpu_idle_dead(); |
| } |
| |
| local_irq_disable(); |
| arch_cpu_idle_enter(); |
| |
| /* |
| * In poll mode we reenable interrupts and spin. |
| * |
| * Also if we detected in the wakeup from idle |
| * path that the tick broadcast device expired |
| * for us, we don't want to go deep idle as we |
| * know that the IPI is going to arrive right |
| * away |
| */ |
| if (cpu_idle_force_poll || tick_check_broadcast_expired()) |
| cpu_idle_poll(); |
| else |
| cpuidle_idle_call(); |
| |
| arch_cpu_idle_exit(); |
| } |
| |
| /* |
| * Since we fell out of the loop above, we know |
| * TIF_NEED_RESCHED must be set, propagate it into |
| * PREEMPT_NEED_RESCHED. |
| * |
| * This is required because for polling idle loops we will |
| * not have had an IPI to fold the state for us. |
| */ |
| preempt_set_need_resched(); |
| tick_nohz_idle_exit(); |
| __current_clr_polling(); |
| |
| /* |
| * We promise to call sched_ttwu_pending and reschedule |
| * if need_resched is set while polling is set. That |
| * means that clearing polling needs to be visible |
| * before doing these things. |
| */ |
| smp_mb__after_atomic(); |
| |
| sched_ttwu_pending(); |
| schedule_preempt_disabled(); |
| } |
| } |
| |
| void cpu_startup_entry(enum cpuhp_state state) |
| { |
| /* |
| * This #ifdef needs to die, but it's too late in the cycle to |
| * make this generic (arm and sh have never invoked the canary |
| * init for the non boot cpus!). Will be fixed in 3.11 |
| */ |
| #ifdef CONFIG_X86 |
| /* |
| * If we're the non-boot CPU, nothing set the stack canary up |
| * for us. The boot CPU already has it initialized but no harm |
| * in doing it again. This is a good place for updating it, as |
| * we wont ever return from this function (so the invalid |
| * canaries already on the stack wont ever trigger). |
| */ |
| boot_init_stack_canary(); |
| #endif |
| arch_cpu_idle_prepare(); |
| cpu_idle_loop(); |
| } |