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