/* * Generic entry point for the idle threads */#include <linux/sched.h>#include <linux/cpu.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_SETUPstatic 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();} /* * 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 {				if (!current_clr_polling_and_test()) {					stop_critical_timings();					rcu_idle_enter();					arch_cpu_idle();					WARN_ON_ONCE(irqs_disabled());					rcu_idle_exit();					start_critical_timings();				} else {					local_irq_enable();				}				__current_set_polling();			}			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();}