static void xen_pv_play_dead(void) /* used only with HOTPLUG_CPU */ { play_dead_common(); HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(smp_processor_id()), NULL); cpu_bringup(); /* * commit 4b0c0f294 (tick: Cleanup NOHZ per cpu data on cpu down) * clears certain data that the cpu_idle loop (which called us * and that we return from) expects. The only way to get that * data back is to call: */ tick_nohz_idle_enter(); tick_nohz_idle_stop_tick_protected(); cpuhp_online_idle(CPUHP_AP_ONLINE_IDLE); }
/* * Generic idle loop implementation * * Called with polling cleared. */ static void do_idle(void) { int cpu = smp_processor_id(); /* * 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(); tick_nohz_idle_enter(); while (!need_resched()) { check_pgt_cache(); rmb(); if (cpu_is_offline(cpu)) { tick_nohz_idle_stop_tick_protected(); cpuhp_report_idle_dead(); 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()) { tick_nohz_idle_restart_tick(); 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_idle(); if (unlikely(klp_patch_pending(current))) klp_update_patch_state(current); }