kernel/sched/idle.c

1 // SPDX-License-Identifier: GPL-2.0-only
7  *        tasks which are handled in sched/fair.c )
14  * sched_idle_set_state - Record idle state for the current CPU.
29 		cpu_idle_force_poll--;  in cpu_idle_poll_ctrl()
85  * default_idle_call - Default CPU idle routine.
111 		return -EBUSY;  in call_cpuidle_s2idle()
121 	 * update no idle residency and return.  in call_cpuidle()
124 		dev->last_residency_ns = 0;  in call_cpuidle()
126 		return -EBUSY;  in call_cpuidle()
132 	 * care of re-enabling the local interrupts  in call_cpuidle()
138  * cpuidle_idle_call - the main idle function
140  * NOTE: no locks or semaphores should be used here
154 	 * case, exit the function after re-enabling the local irq.  in cpuidle_idle_call()
163 	 * section, so no more rcu read side critical sections and one more  in cpuidle_idle_call()
175 	 * Suspend-to-idle ("s2idle") is a system state in which all user space  in cpuidle_idle_call()
177 	 * activity happens here and in interrupts (if any). In that case bypass  in cpuidle_idle_call()
179 	 * available.  Possibly also suspend the local tick and the entire  in cpuidle_idle_call()
184 	if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {  in cpuidle_idle_call()
195 			max_latency_ns = dev->forced_idle_latency_limit_ns;  in cpuidle_idle_call()
249 	 * Our polling bit is clear if we're not scheduled (i.e. if rq->curr !=  in do_idle()
250 	 * rq->idle). This means that, if rq->idle has the polling bit set,  in do_idle()
273 		 * In poll mode we reenable interrupts and spin. Also if we  in do_idle()
274 		 * detected in the wakeup from idle path that the tick  in do_idle()
306 	 * RCU relies on this call to be done outside of an RCU read-side  in do_idle()
331 	WRITE_ONCE(it->done, 1);  in idle_inject_timer_fn()
342 	 * Only FIFO tasks can disable the tick since they don't need the forced  in play_idle_precise()
345 	WARN_ON_ONCE(current->policy != SCHED_FIFO);  in play_idle_precise()
346 	WARN_ON_ONCE(current->nr_cpus_allowed != 1);  in play_idle_precise()
347 	WARN_ON_ONCE(!(current->flags & PF_KTHREAD));  in play_idle_precise()
348 	WARN_ON_ONCE(!(current->flags & PF_NO_SETAFFINITY));  in play_idle_precise()
350 	WARN_ON_ONCE(current->mm);  in play_idle_precise()
354 	current->flags |= PF_IDLE;  in play_idle_precise()
367 	current->flags &= ~PF_IDLE;  in play_idle_precise()
376 	current->flags |= PF_IDLE;  in cpu_startup_entry()
384  * idle-task scheduling class.
416 	schedstat_inc(rq->sched_goidle);  in set_next_task_idle()
422 	return rq->idle;  in pick_task_idle()
428 	struct task_struct *next = rq->idle;  in pick_next_task_idle()
436  * It is not legal to sleep in the idle task - print a warning
449  * scheduler tick hitting a task of our scheduling class.
451  * NOTE: This function can be called remotely by the tick offload that
452  * goes along full dynticks. Therefore no local assumption can be made
453  * and everything must be accessed through the @rq and @curr passed in
476  * Simple, special scheduling class for the per-CPU idle tasks:
480 	/* no enqueue/yield_task for idle tasks */