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[PATCH] tick-management: core functionality
With Ingo Molnar <mingo@elte.hu> The tick-management code is the first user of the clockevents layer. It takes clock event devices from the clock events core and uses them to provide the periodic tick. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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31
include/linux/tick.h
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31
include/linux/tick.h
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@ -0,0 +1,31 @@
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/* linux/include/linux/tick.h
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*
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* This file contains the structure definitions for tick related functions
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*
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*/
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#ifndef _LINUX_TICK_H
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#define _LINUX_TICK_H
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#include <linux/clockchips.h>
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#ifdef CONFIG_GENERIC_CLOCKEVENTS
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enum tick_device_mode {
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TICKDEV_MODE_PERIODIC,
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TICKDEV_MODE_ONESHOT,
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};
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struct tick_device {
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struct clock_event_device *evtdev;
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enum tick_device_mode mode;
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};
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extern void __init tick_init(void);
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#else
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static inline void tick_init(void) { }
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#endif
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#endif
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@ -40,6 +40,7 @@
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#include <linux/cpu.h>
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#include <linux/cpuset.h>
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#include <linux/efi.h>
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#include <linux/tick.h>
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#include <linux/taskstats_kern.h>
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#include <linux/delayacct.h>
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#include <linux/unistd.h>
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@ -515,6 +516,7 @@ asmlinkage void __init start_kernel(void)
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* enable them
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*/
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lock_kernel();
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tick_init();
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boot_cpu_init();
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page_address_init();
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printk(KERN_NOTICE);
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@ -1,3 +1,4 @@
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obj-y += ntp.o clocksource.o jiffies.o
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obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
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obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
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obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
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277
kernel/time/tick-common.c
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kernel/time/tick-common.c
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/*
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* linux/kernel/time/tick-common.c
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*
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* This file contains the base functions to manage periodic tick
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* related events.
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*
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* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
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* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
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*
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* This code is licenced under the GPL version 2. For details see
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* kernel-base/COPYING.
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/hrtimer.h>
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#include <linux/irq.h>
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#include <linux/percpu.h>
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#include <linux/profile.h>
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#include <linux/sched.h>
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#include <linux/tick.h>
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/*
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* Tick devices
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*/
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static DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
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/*
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* Tick next event: keeps track of the tick time
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*/
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static ktime_t tick_next_period;
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static ktime_t tick_period;
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static int tick_do_timer_cpu = -1;
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static DEFINE_SPINLOCK(tick_device_lock);
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/*
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* Periodic tick
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*/
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static void tick_periodic(int cpu)
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{
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if (tick_do_timer_cpu == cpu) {
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write_seqlock(&xtime_lock);
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/* Keep track of the next tick event */
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tick_next_period = ktime_add(tick_next_period, tick_period);
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do_timer(1);
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write_sequnlock(&xtime_lock);
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}
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update_process_times(user_mode(get_irq_regs()));
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profile_tick(CPU_PROFILING);
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}
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/*
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* Event handler for periodic ticks
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*/
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void tick_handle_periodic(struct clock_event_device *dev)
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{
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int cpu = smp_processor_id();
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tick_periodic(cpu);
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if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
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return;
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/*
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* Setup the next period for devices, which do not have
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* periodic mode:
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*/
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for (;;) {
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ktime_t next = ktime_add(dev->next_event, tick_period);
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if (!clockevents_program_event(dev, next, ktime_get()))
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return;
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tick_periodic(cpu);
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}
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}
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/*
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* Setup the device for a periodic tick
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*/
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void tick_setup_periodic(struct clock_event_device *dev)
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{
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dev->event_handler = tick_handle_periodic;
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if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
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clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
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} else {
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unsigned long seq;
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ktime_t next;
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do {
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seq = read_seqbegin(&xtime_lock);
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next = tick_next_period;
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} while (read_seqretry(&xtime_lock, seq));
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clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
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for (;;) {
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if (!clockevents_program_event(dev, next, ktime_get()))
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return;
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next = ktime_add(next, tick_period);
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}
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}
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}
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/*
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* Setup the tick device
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*/
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static void tick_setup_device(struct tick_device *td,
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struct clock_event_device *newdev, int cpu,
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cpumask_t cpumask)
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{
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ktime_t next_event;
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void (*handler)(struct clock_event_device *) = NULL;
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/*
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* First device setup ?
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*/
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if (!td->evtdev) {
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/*
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* If no cpu took the do_timer update, assign it to
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* this cpu:
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*/
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if (tick_do_timer_cpu == -1) {
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tick_do_timer_cpu = cpu;
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tick_next_period = ktime_get();
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tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
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}
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/*
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* Startup in periodic mode first.
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*/
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td->mode = TICKDEV_MODE_PERIODIC;
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} else {
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handler = td->evtdev->event_handler;
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next_event = td->evtdev->next_event;
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}
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td->evtdev = newdev;
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/*
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* When the device is not per cpu, pin the interrupt to the
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* current cpu:
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*/
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if (!cpus_equal(newdev->cpumask, cpumask))
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irq_set_affinity(newdev->irq, cpumask);
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if (td->mode == TICKDEV_MODE_PERIODIC)
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tick_setup_periodic(newdev, 0);
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}
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/*
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* Check, if the new registered device should be used.
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*/
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static int tick_check_new_device(struct clock_event_device *newdev)
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{
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struct clock_event_device *curdev;
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struct tick_device *td;
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int cpu, ret = NOTIFY_OK;
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unsigned long flags;
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cpumask_t cpumask;
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spin_lock_irqsave(&tick_device_lock, flags);
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cpu = smp_processor_id();
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if (!cpu_isset(cpu, newdev->cpumask))
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goto out;
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td = &per_cpu(tick_cpu_device, cpu);
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curdev = td->evtdev;
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cpumask = cpumask_of_cpu(cpu);
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/* cpu local device ? */
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if (!cpus_equal(newdev->cpumask, cpumask)) {
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/*
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* If the cpu affinity of the device interrupt can not
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* be set, ignore it.
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*/
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if (!irq_can_set_affinity(newdev->irq))
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goto out_bc;
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/*
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* If we have a cpu local device already, do not replace it
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* by a non cpu local device
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*/
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if (curdev && cpus_equal(curdev->cpumask, cpumask))
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goto out_bc;
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}
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/*
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* If we have an active device, then check the rating and the oneshot
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* feature.
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*/
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if (curdev) {
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/*
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* Check the rating
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*/
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if (curdev->rating >= newdev->rating)
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goto out;
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}
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/*
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* Replace the eventually existing device by the new
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* device.
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*/
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clockevents_exchange_device(curdev, newdev);
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tick_setup_device(td, newdev, cpu, cpumask);
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ret = NOTIFY_STOP;
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out:
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spin_unlock_irqrestore(&tick_device_lock, flags);
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return ret;
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}
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/*
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* Shutdown an event device on a given cpu:
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*
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* This is called on a life CPU, when a CPU is dead. So we cannot
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* access the hardware device itself.
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* We just set the mode and remove it from the lists.
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*/
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static void tick_shutdown(unsigned int *cpup)
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{
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struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
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struct clock_event_device *dev = td->evtdev;
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unsigned long flags;
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spin_lock_irqsave(&tick_device_lock, flags);
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td->mode = TICKDEV_MODE_PERIODIC;
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if (dev) {
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/*
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* Prevent that the clock events layer tries to call
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* the set mode function!
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*/
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dev->mode = CLOCK_EVT_MODE_UNUSED;
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clockevents_exchange_device(dev, NULL);
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td->evtdev = NULL;
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}
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spin_unlock_irqrestore(&tick_device_lock, flags);
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}
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/*
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* Notification about clock event devices
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*/
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static int tick_notify(struct notifier_block *nb, unsigned long reason,
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void *dev)
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{
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switch (reason) {
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case CLOCK_EVT_NOTIFY_ADD:
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return tick_check_new_device(dev);
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case CLOCK_EVT_NOTIFY_CPU_DEAD:
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tick_shutdown(dev);
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break;
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default:
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break;
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}
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return NOTIFY_OK;
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}
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static struct notifier_block tick_notifier = {
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.notifier_call = tick_notify,
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};
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/**
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* tick_init - initialize the tick control
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*
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* Register the notifier with the clockevents framework
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*/
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void __init tick_init(void)
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{
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clockevents_register_notifier(&tick_notifier);
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}
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