1 files changed, 524 insertions, 0 deletions
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
new file mode 100644
index 000000000..200a0fac0
--- /dev/null
+++ b/kernel/sched/idle.c
@@ -0,0 +1,524 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic entry points for the idle threads and
+ * implementation of the idle task scheduling class.
+ *
+ * (NOTE: these are not related to SCHED_IDLE batch scheduled
+ *        tasks which are handled in sched/fair.c )
+ */
+
+/* Linker adds these: start and end of __cpuidle functions */
+extern char __cpuidle_text_start[], __cpuidle_text_end[];
+
+/**
+ * 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)
+{
+	idle_set_state(this_rq(), idle_state);
+}
+
+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 noinline int __cpuidle cpu_idle_poll(void)
+{
+	trace_cpu_idle(0, smp_processor_id());
+	stop_critical_timings();
+	ct_idle_enter();
+	local_irq_enable();
+
+	while (!tif_need_resched() &&
+	       (cpu_idle_force_poll || tick_check_broadcast_expired()))
+		cpu_relax();
+
+	ct_idle_exit();
+	start_critical_timings();
+	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
+
+	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;
+	raw_local_irq_enable();
+}
+
+/**
+ * default_idle_call - Default CPU idle routine.
+ *
+ * To use when the cpuidle framework cannot be used.
+ */
+void __cpuidle default_idle_call(void)
+{
+	if (current_clr_polling_and_test()) {
+		local_irq_enable();
+	} else {
+
+		trace_cpu_idle(1, smp_processor_id());
+		stop_critical_timings();
+
+		/*
+		 * arch_cpu_idle() is supposed to enable IRQs, however
+		 * we can't do that because of RCU and tracing.
+		 *
+		 * Trace IRQs enable here, then switch off RCU, and have
+		 * arch_cpu_idle() use raw_local_irq_enable(). Note that
+		 * ct_idle_enter() relies on lockdep IRQ state, so switch that
+		 * last -- this is very similar to the entry code.
+		 */
+		trace_hardirqs_on_prepare();
+		lockdep_hardirqs_on_prepare();
+		ct_idle_enter();
+		lockdep_hardirqs_on(_THIS_IP_);
+
+		arch_cpu_idle();
+
+		/*
+		 * OK, so IRQs are enabled here, but RCU needs them disabled to
+		 * turn itself back on.. funny thing is that disabling IRQs
+		 * will cause tracing, which needs RCU. Jump through hoops to
+		 * make it 'work'.
+		 */
+		raw_local_irq_disable();
+		lockdep_hardirqs_off(_THIS_IP_);
+		ct_idle_exit();
+		lockdep_hardirqs_on(_THIS_IP_);
+		raw_local_irq_enable();
+
+		start_critical_timings();
+		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
+	}
+}
+
+static int call_cpuidle_s2idle(struct cpuidle_driver *drv,
+			       struct cpuidle_device *dev)
+{
+	if (current_clr_polling_and_test())
+		return -EBUSY;
+
+	return cpuidle_enter_s2idle(drv, dev);
+}
+
+static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
+		      int 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_ns = 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 architectures 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;
+	}
+
+	/*
+	 * The RCU framework needs to be told that we are entering an idle
+	 * section, so no more rcu read side critical sections and one more
+	 * step to the grace period
+	 */
+
+	if (cpuidle_not_available(drv, dev)) {
+		tick_nohz_idle_stop_tick();
+
+		default_idle_call();
+		goto exit_idle;
+	}
+
+	/*
+	 * Suspend-to-idle ("s2idle") 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 interrupts (if any). In that case bypass
+	 * the cpuidle governor and go straight 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_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
+		u64 max_latency_ns;
+
+		if (idle_should_enter_s2idle()) {
+
+			entered_state = call_cpuidle_s2idle(drv, dev);
+			if (entered_state > 0)
+				goto exit_idle;
+
+			max_latency_ns = U64_MAX;
+		} else {
+			max_latency_ns = dev->forced_idle_latency_limit_ns;
+		}
+
+		tick_nohz_idle_stop_tick();
+
+		next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
+		call_cpuidle(drv, dev, next_state);
+	} else {
+		bool stop_tick = true;
+
+		/*
+		 * Ask the cpuidle framework to choose a convenient idle state.
+		 */
+		next_state = cpuidle_select(drv, dev, &stop_tick);
+
+		if (stop_tick || tick_nohz_tick_stopped())
+			tick_nohz_idle_stop_tick();
+		else
+			tick_nohz_idle_retain_tick();
+
+		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();
+}
+
+/*
+ * Generic idle loop implementation
+ *
+ * Called with polling cleared.
+ */
+static void do_idle(void)
+{
+	int cpu = smp_processor_id();
+
+	/*
+	 * Check if we need to update blocked load
+	 */
+	nohz_run_idle_balance(cpu);
+
+	/*
+	 * 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()) {
+		rmb();
+
+		local_irq_disable();
+
+		if (cpu_is_offline(cpu)) {
+			tick_nohz_idle_stop_tick();
+			cpuhp_report_idle_dead();
+			arch_cpu_idle_dead();
+		}
+
+		arch_cpu_idle_enter();
+		rcu_nocb_flush_deferred_wakeup();
+
+		/*
+		 * 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();
+
+	/*
+	 * RCU relies on this call to be done outside of an RCU read-side
+	 * critical section.
+	 */
+	flush_smp_call_function_queue();
+	schedule_idle();
+
+	if (unlikely(klp_patch_pending(current)))
+		klp_update_patch_state(current);
+}
+
+bool cpu_in_idle(unsigned long pc)
+{
+	return pc >= (unsigned long)__cpuidle_text_start &&
+		pc < (unsigned long)__cpuidle_text_end;
+}
+
+struct idle_timer {
+	struct hrtimer timer;
+	int done;
+};
+
+static enum hrtimer_restart idle_inject_timer_fn(struct hrtimer *timer)
+{
+	struct idle_timer *it = container_of(timer, struct idle_timer, timer);
+
+	WRITE_ONCE(it->done, 1);
+	set_tsk_need_resched(current);
+
+	return HRTIMER_NORESTART;
+}
+
+void play_idle_precise(u64 duration_ns, u64 latency_ns)
+{
+	struct idle_timer it;
+
+	/*
+	 * Only FIFO tasks can disable the tick since they don't need the forced
+	 * preemption.
+	 */
+	WARN_ON_ONCE(current->policy != SCHED_FIFO);
+	WARN_ON_ONCE(current->nr_cpus_allowed != 1);
+	WARN_ON_ONCE(!(current->flags & PF_KTHREAD));
+	WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));
+	WARN_ON_ONCE(!duration_ns);
+	WARN_ON_ONCE(current->mm);
+
+	rcu_sleep_check();
+	preempt_disable();
+	current->flags |= PF_IDLE;
+	cpuidle_use_deepest_state(latency_ns);
+
+	it.done = 0;
+	hrtimer_init_on_stack(&it.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
+	it.timer.function = idle_inject_timer_fn;
+	hrtimer_start(&it.timer, ns_to_ktime(duration_ns),
+		      HRTIMER_MODE_REL_PINNED_HARD);
+
+	while (!READ_ONCE(it.done))
+		do_idle();
+
+	cpuidle_use_deepest_state(0);
+	current->flags &= ~PF_IDLE;
+
+	preempt_fold_need_resched();
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(play_idle_precise);
+
+void cpu_startup_entry(enum cpuhp_state state)
+{
+	current->flags |= PF_IDLE;
+	arch_cpu_idle_prepare();
+	cpuhp_online_idle(state);
+	while (1)
+		do_idle();
+}
+
+/*
+ * idle-task scheduling class.
+ */
+
+#ifdef CONFIG_SMP
+static int
+select_task_rq_idle(struct task_struct *p, int cpu, int flags)
+{
+	return task_cpu(p); /* IDLE tasks as never migrated */
+}
+
+static int
+balance_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
+{
+	return WARN_ON_ONCE(1);
+}
+#endif
+
+/*
+ * Idle tasks are unconditionally rescheduled:
+ */
+static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int flags)
+{
+	resched_curr(rq);
+}
+
+static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
+{
+}
+
+static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first)
+{
+	update_idle_core(rq);
+	schedstat_inc(rq->sched_goidle);
+}
+
+#ifdef CONFIG_SMP
+static struct task_struct *pick_task_idle(struct rq *rq)
+{
+	return rq->idle;
+}
+#endif
+
+struct task_struct *pick_next_task_idle(struct rq *rq)
+{
+	struct task_struct *next = rq->idle;
+
+	set_next_task_idle(rq, next, true);
+
+	return next;
+}
+
+/*
+ * It is not legal to sleep in the idle task - print a warning
+ * message if some code attempts to do it:
+ */
+static void
+dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)
+{
+	raw_spin_rq_unlock_irq(rq);
+	printk(KERN_ERR "bad: scheduling from the idle thread!\n");
+	dump_stack();
+	raw_spin_rq_lock_irq(rq);
+}
+
+/*
+ * scheduler tick hitting a task of our scheduling class.
+ *
+ * NOTE: This function can be called remotely by the tick offload that
+ * goes along full dynticks. Therefore no local assumption can be made
+ * and everything must be accessed through the @rq and @curr passed in
+ * parameters.
+ */
+static void task_tick_idle(struct rq *rq, struct task_struct *curr, int queued)
+{
+}
+
+static void switched_to_idle(struct rq *rq, struct task_struct *p)
+{
+	BUG();
+}
+
+static void
+prio_changed_idle(struct rq *rq, struct task_struct *p, int oldprio)
+{
+	BUG();
+}
+
+static void update_curr_idle(struct rq *rq)
+{
+}
+
+/*
+ * Simple, special scheduling class for the per-CPU idle tasks:
+ */
+DEFINE_SCHED_CLASS(idle) = {
+
+	/* no enqueue/yield_task for idle tasks */
+
+	/* dequeue is not valid, we print a debug message there: */
+	.dequeue_task		= dequeue_task_idle,
+
+	.check_preempt_curr	= check_preempt_curr_idle,
+
+	.pick_next_task		= pick_next_task_idle,
+	.put_prev_task		= put_prev_task_idle,
+	.set_next_task          = set_next_task_idle,
+
+#ifdef CONFIG_SMP
+	.balance		= balance_idle,
+	.pick_task		= pick_task_idle,
+	.select_task_rq		= select_task_rq_idle,
+	.set_cpus_allowed	= set_cpus_allowed_common,
+#endif
+
+	.task_tick		= task_tick_idle,
+
+	.prio_changed		= prio_changed_idle,
+	.switched_to		= switched_to_idle,
+	.update_curr		= update_curr_idle,
+};