![Rafael J. Wysocki](/assets/img/avatar_default.png)
The check of the cpuidle_enter() return value against -EBUSY made in call_cpuidle() will not be necessary any more if cpuidle_enter_state() calls default_idle_call() directly when it is about to return -EBUSY, so make that happen and eliminate the check. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Tested-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Tested-by: Sudeep Holla <sudeep.holla@arm.com> Acked-by: Kevin Hilman <khilman@linaro.org>
303 lines
7.4 KiB
C
303 lines
7.4 KiB
C
/*
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* Generic entry point for the idle threads
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*/
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#include <linux/sched.h>
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#include <linux/cpu.h>
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#include <linux/cpuidle.h>
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#include <linux/tick.h>
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#include <linux/mm.h>
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#include <linux/stackprotector.h>
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#include <linux/suspend.h>
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#include <asm/tlb.h>
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#include <trace/events/power.h>
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#include "sched.h"
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/**
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* sched_idle_set_state - Record idle state for the current CPU.
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* @idle_state: State to record.
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*/
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void sched_idle_set_state(struct cpuidle_state *idle_state)
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{
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idle_set_state(this_rq(), idle_state);
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}
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static int __read_mostly cpu_idle_force_poll;
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void cpu_idle_poll_ctrl(bool enable)
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{
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if (enable) {
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cpu_idle_force_poll++;
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} else {
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cpu_idle_force_poll--;
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WARN_ON_ONCE(cpu_idle_force_poll < 0);
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}
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}
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#ifdef CONFIG_GENERIC_IDLE_POLL_SETUP
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static int __init cpu_idle_poll_setup(char *__unused)
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{
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cpu_idle_force_poll = 1;
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return 1;
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}
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__setup("nohlt", cpu_idle_poll_setup);
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static int __init cpu_idle_nopoll_setup(char *__unused)
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{
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cpu_idle_force_poll = 0;
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return 1;
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}
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__setup("hlt", cpu_idle_nopoll_setup);
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#endif
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static inline int cpu_idle_poll(void)
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{
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rcu_idle_enter();
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trace_cpu_idle_rcuidle(0, smp_processor_id());
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local_irq_enable();
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while (!tif_need_resched() &&
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(cpu_idle_force_poll || tick_check_broadcast_expired()))
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cpu_relax();
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trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
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rcu_idle_exit();
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return 1;
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}
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/* Weak implementations for optional arch specific functions */
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void __weak arch_cpu_idle_prepare(void) { }
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void __weak arch_cpu_idle_enter(void) { }
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void __weak arch_cpu_idle_exit(void) { }
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void __weak arch_cpu_idle_dead(void) { }
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void __weak arch_cpu_idle(void)
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{
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cpu_idle_force_poll = 1;
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local_irq_enable();
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}
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/**
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* default_idle_call - Default CPU idle routine.
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*
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* To use when the cpuidle framework cannot be used.
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*/
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void default_idle_call(void)
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{
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if (current_clr_polling_and_test())
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local_irq_enable();
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else
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arch_cpu_idle();
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}
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static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
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int next_state)
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{
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/* Fall back to the default arch idle method on errors. */
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if (next_state < 0) {
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default_idle_call();
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return next_state;
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}
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/*
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* The idle task must be scheduled, it is pointless to go to idle, just
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* update no idle residency and return.
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*/
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if (current_clr_polling_and_test()) {
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dev->last_residency = 0;
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local_irq_enable();
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return -EBUSY;
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}
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/*
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* Enter the idle state previously returned by the governor decision.
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* This function will block until an interrupt occurs and will take
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* care of re-enabling the local interrupts
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*/
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return cpuidle_enter(drv, dev, next_state);
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}
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/**
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* cpuidle_idle_call - the main idle function
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*
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* NOTE: no locks or semaphores should be used here
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*
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* On archs that support TIF_POLLING_NRFLAG, is called with polling
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* set, and it returns with polling set. If it ever stops polling, it
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* must clear the polling bit.
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*/
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static void cpuidle_idle_call(void)
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{
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struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
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struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
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int next_state, entered_state;
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/*
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* Check if the idle task must be rescheduled. If it is the
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* case, exit the function after re-enabling the local irq.
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*/
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if (need_resched()) {
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local_irq_enable();
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return;
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}
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/*
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* During the idle period, stop measuring the disabled irqs
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* critical sections latencies
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*/
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stop_critical_timings();
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/*
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* Tell the RCU framework we are entering an idle section,
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* so no more rcu read side critical sections and one more
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* step to the grace period
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*/
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rcu_idle_enter();
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if (cpuidle_not_available(drv, dev)) {
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default_idle_call();
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goto exit_idle;
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}
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/*
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* Suspend-to-idle ("freeze") is a system state in which all user space
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* has been frozen, all I/O devices have been suspended and the only
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* activity happens here and in iterrupts (if any). In that case bypass
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* the cpuidle governor and go stratight for the deepest idle state
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* available. Possibly also suspend the local tick and the entire
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* timekeeping to prevent timer interrupts from kicking us out of idle
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* until a proper wakeup interrupt happens.
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*/
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if (idle_should_freeze()) {
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entered_state = cpuidle_enter_freeze(drv, dev);
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if (entered_state >= 0) {
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local_irq_enable();
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goto exit_idle;
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}
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next_state = cpuidle_find_deepest_state(drv, dev);
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call_cpuidle(drv, dev, next_state);
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} else {
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/*
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* Ask the cpuidle framework to choose a convenient idle state.
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*/
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next_state = cpuidle_select(drv, dev);
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entered_state = call_cpuidle(drv, dev, next_state);
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/*
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* Give the governor an opportunity to reflect on the outcome
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*/
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cpuidle_reflect(dev, entered_state);
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}
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exit_idle:
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__current_set_polling();
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/*
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* It is up to the idle functions to reenable local interrupts
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*/
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if (WARN_ON_ONCE(irqs_disabled()))
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local_irq_enable();
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rcu_idle_exit();
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start_critical_timings();
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}
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DEFINE_PER_CPU(bool, cpu_dead_idle);
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/*
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* Generic idle loop implementation
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*
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* Called with polling cleared.
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*/
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static void cpu_idle_loop(void)
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{
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while (1) {
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/*
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* If the arch has a polling bit, we maintain an invariant:
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*
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* Our polling bit is clear if we're not scheduled (i.e. if
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* rq->curr != rq->idle). This means that, if rq->idle has
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* the polling bit set, then setting need_resched is
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* guaranteed to cause the cpu to reschedule.
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*/
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__current_set_polling();
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tick_nohz_idle_enter();
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while (!need_resched()) {
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check_pgt_cache();
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rmb();
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if (cpu_is_offline(smp_processor_id())) {
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rcu_cpu_notify(NULL, CPU_DYING_IDLE,
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(void *)(long)smp_processor_id());
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smp_mb(); /* all activity before dead. */
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this_cpu_write(cpu_dead_idle, true);
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arch_cpu_idle_dead();
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}
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local_irq_disable();
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arch_cpu_idle_enter();
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/*
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* In poll mode we reenable interrupts and spin.
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*
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* Also if we detected in the wakeup from idle
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* path that the tick broadcast device expired
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* for us, we don't want to go deep idle as we
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* know that the IPI is going to arrive right
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* away
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*/
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if (cpu_idle_force_poll || tick_check_broadcast_expired())
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cpu_idle_poll();
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else
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cpuidle_idle_call();
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arch_cpu_idle_exit();
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}
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/*
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* Since we fell out of the loop above, we know
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* TIF_NEED_RESCHED must be set, propagate it into
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* PREEMPT_NEED_RESCHED.
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*
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* This is required because for polling idle loops we will
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* not have had an IPI to fold the state for us.
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*/
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preempt_set_need_resched();
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tick_nohz_idle_exit();
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__current_clr_polling();
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/*
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* We promise to call sched_ttwu_pending and reschedule
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* if need_resched is set while polling is set. That
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* means that clearing polling needs to be visible
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* before doing these things.
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*/
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smp_mb__after_atomic();
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sched_ttwu_pending();
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schedule_preempt_disabled();
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}
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}
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void cpu_startup_entry(enum cpuhp_state state)
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{
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/*
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* This #ifdef needs to die, but it's too late in the cycle to
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* make this generic (arm and sh have never invoked the canary
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* init for the non boot cpus!). Will be fixed in 3.11
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*/
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#ifdef CONFIG_X86
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/*
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* If we're the non-boot CPU, nothing set the stack canary up
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* for us. The boot CPU already has it initialized but no harm
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* in doing it again. This is a good place for updating it, as
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* we wont ever return from this function (so the invalid
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* canaries already on the stack wont ever trigger).
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*/
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boot_init_stack_canary();
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#endif
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arch_cpu_idle_prepare();
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cpu_idle_loop();
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}
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