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/*
* Generic entry point for the idle threads
*/
#include <linux/sched.h>
#include <linux/cpu.h>
#include <linux/cpuidle.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_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 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_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();
}
/**
* cpuidle_idle_call - the main idle function
*
* NOTE: no locks or semaphores should be used here
* return non-zero on failure
*/
static int cpuidle_idle_call(void)
{
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
int next_state, entered_state;
/*
* 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())
return cpu_idle_poll();
/*
* Check if the idle task must rescheduled. If it is the case,
* exit the function after re-enabling the local irq and set
* again the polling flag
*/
if (current_clr_polling_and_test()) {
local_irq_enable();
__current_set_polling();
return 0;
}
/*
* During the idle period, stop measuring the disabled irqs
* critical sections latencies
*/
stop_critical_timings();
/*
* Tell the RCU framework we are entering an idle section,
* so no more rcu read side critical sections and one more
* step to the grace period
*/
rcu_idle_enter();
/*
* Ask the governor to choose an idle state it thinks it is
* convenient to go to. There is *always* a convenient idle
* state but the call could fail if cpuidle is not enabled
*/
next_state = cpuidle_select(drv, dev);
if (next_state < 0) {
arch_cpu_idle();
goto out;
}
/*
* The idle task must be scheduled, it is pointless to go to idle,
* just update no idle residency and get out of this function
*/
if (need_resched()) {
dev->last_residency = 0;
/* give the governor an opportunity to reflect on the outcome */
cpuidle_reflect(dev, next_state);
local_irq_enable();
goto out;
}
trace_cpu_idle_rcuidle(next_state, dev->cpu);
/*
* 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
*/
entered_state = cpuidle_enter(drv, dev, next_state);
trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
/* give the governor an opportunity to reflect on the outcome */
cpuidle_reflect(dev, entered_state);
out:
WARN_ON_ONCE(irqs_disabled());
rcu_idle_exit();
start_critical_timings();
__current_set_polling();
return 0;
}
/*
* 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();
/*
* It is up to the underlying functions to
* enable the local interrupts again
*/
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();
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();
cpu_idle_loop();
}
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