| /* |
| * 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 <asm/tlb.h> |
| |
| #include <trace/events/power.h> |
| |
| 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(); |
| while (!tif_need_resched()) |
| cpu_relax(); |
| 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(); |
| } |
| |
| /** |
| * cpuidle_idle_call - the main idle function |
| * |
| * NOTE: no locks or semaphores should be used here |
| * return non-zero on failure |
| */ |
| static int cpuidle_idle_call(void) |
| { |
| struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); |
| struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev); |
| int next_state, entered_state, ret; |
| bool broadcast; |
| |
| /* |
| * Check if the idle task must be rescheduled. If it is the |
| * case, exit the function after re-enabling the local irq and |
| * set again the polling flag |
| */ |
| if (current_clr_polling_and_test()) { |
| local_irq_enable(); |
| __current_set_polling(); |
| return 0; |
| } |
| |
| /* |
| * During the idle period, stop measuring the disabled irqs |
| * critical sections latencies |
| */ |
| stop_critical_timings(); |
| |
| /* |
| * 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(); |
| |
| /* |
| * Ask the cpuidle framework to choose a convenient idle state. |
| * Fall back to the default arch specific idle method on errors. |
| */ |
| next_state = cpuidle_select(drv, dev); |
| |
| ret = next_state; |
| if (ret >= 0) { |
| /* |
| * The idle task must be scheduled, it is pointless to |
| * go to idle, just update no idle residency and get |
| * out of this function |
| */ |
| if (current_clr_polling_and_test()) { |
| dev->last_residency = 0; |
| entered_state = next_state; |
| local_irq_enable(); |
| } else { |
| broadcast = !!(drv->states[next_state].flags & |
| CPUIDLE_FLAG_TIMER_STOP); |
| |
| if (broadcast) |
| /* |
| * Tell the time framework to switch |
| * to a broadcast timer because our |
| * local timer will be shutdown. If a |
| * local timer is used from another |
| * cpu as a broadcast timer, this call |
| * may fail if it is not available |
| */ |
| ret = clockevents_notify( |
| CLOCK_EVT_NOTIFY_BROADCAST_ENTER, |
| &dev->cpu); |
| |
| if (ret >= 0) { |
| trace_cpu_idle_rcuidle(next_state, dev->cpu); |
| |
| /* |
| * 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 |
| */ |
| entered_state = cpuidle_enter(drv, dev, |
| next_state); |
| |
| trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, |
| dev->cpu); |
| |
| if (broadcast) |
| clockevents_notify( |
| CLOCK_EVT_NOTIFY_BROADCAST_EXIT, |
| &dev->cpu); |
| |
| /* |
| * Give the governor an opportunity to reflect on the |
| * outcome |
| */ |
| cpuidle_reflect(dev, entered_state); |
| } |
| } |
| } |
| |
| /* |
| * We can't use the cpuidle framework, let's use the default |
| * idle routine |
| */ |
| if (ret < 0) |
| arch_cpu_idle(); |
| |
| __current_set_polling(); |
| |
| /* |
| * It is up to the idle functions to enable back the local |
| * interrupt |
| */ |
| if (WARN_ON_ONCE(irqs_disabled())) |
| local_irq_enable(); |
| |
| rcu_idle_exit(); |
| start_critical_timings(); |
| |
| return 0; |
| } |
| |
| /* |
| * Generic idle loop implementation |
| */ |
| static void cpu_idle_loop(void) |
| { |
| while (1) { |
| tick_nohz_idle_enter(); |
| |
| while (!need_resched()) { |
| check_pgt_cache(); |
| rmb(); |
| |
| if (cpu_is_offline(smp_processor_id())) |
| 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(); |
| 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 |
| __current_set_polling(); |
| arch_cpu_idle_prepare(); |
| cpu_idle_loop(); |
| } |