idle.c
3.29 KB
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/*
* The idle loop for all SuperH platforms.
*
* Copyright (C) 2002 - 2009 Paul Mundt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/pm.h>
#include <linux/tick.h>
#include <linux/preempt.h>
#include <linux/thread_info.h>
#include <linux/irqflags.h>
#include <linux/smp.h>
#include <linux/cpuidle.h>
#include <asm/pgalloc.h>
#include <asm/system.h>
#include <linux/atomic.h>
#include <asm/smp.h>
void (*pm_idle)(void);
static int hlt_counter;
static int __init nohlt_setup(char *__unused)
{
hlt_counter = 1;
return 1;
}
__setup("nohlt", nohlt_setup);
static int __init hlt_setup(char *__unused)
{
hlt_counter = 0;
return 1;
}
__setup("hlt", hlt_setup);
static inline int hlt_works(void)
{
return !hlt_counter;
}
/*
* On SMP it's slightly faster (but much more power-consuming!)
* to poll the ->work.need_resched flag instead of waiting for the
* cross-CPU IPI to arrive. Use this option with caution.
*/
static void poll_idle(void)
{
local_irq_enable();
while (!need_resched())
cpu_relax();
}
void default_idle(void)
{
if (hlt_works()) {
clear_thread_flag(TIF_POLLING_NRFLAG);
smp_mb__after_clear_bit();
set_bl_bit();
if (!need_resched()) {
local_irq_enable();
cpu_sleep();
} else
local_irq_enable();
set_thread_flag(TIF_POLLING_NRFLAG);
clear_bl_bit();
} else
poll_idle();
}
/*
* The idle thread. There's no useful work to be done, so just try to conserve
* power and have a low exit latency (ie sit in a loop waiting for somebody to
* say that they'd like to reschedule)
*/
void cpu_idle(void)
{
unsigned int cpu = smp_processor_id();
set_thread_flag(TIF_POLLING_NRFLAG);
/* endless idle loop with no priority at all */
while (1) {
tick_nohz_idle_enter();
rcu_idle_enter();
while (!need_resched()) {
check_pgt_cache();
rmb();
if (cpu_is_offline(cpu))
play_dead();
local_irq_disable();
/* Don't trace irqs off for idle */
stop_critical_timings();
if (cpuidle_idle_call())
pm_idle();
/*
* Sanity check to ensure that pm_idle() returns
* with IRQs enabled
*/
WARN_ON(irqs_disabled());
start_critical_timings();
}
rcu_idle_exit();
tick_nohz_idle_exit();
preempt_enable_no_resched();
schedule();
preempt_disable();
}
}
void __init select_idle_routine(void)
{
/*
* If a platform has set its own idle routine, leave it alone.
*/
if (pm_idle)
return;
if (hlt_works())
pm_idle = default_idle;
else
pm_idle = poll_idle;
}
static void do_nothing(void *unused)
{
}
void stop_this_cpu(void *unused)
{
local_irq_disable();
set_cpu_online(smp_processor_id(), false);
for (;;)
cpu_sleep();
}
/*
* cpu_idle_wait - Used to ensure that all the CPUs discard old value of
* pm_idle and update to new pm_idle value. Required while changing pm_idle
* handler on SMP systems.
*
* Caller must have changed pm_idle to the new value before the call. Old
* pm_idle value will not be used by any CPU after the return of this function.
*/
void cpu_idle_wait(void)
{
smp_mb();
/* kick all the CPUs so that they exit out of pm_idle */
smp_call_function(do_nothing, NULL, 1);
}
EXPORT_SYMBOL_GPL(cpu_idle_wait);