linux/kernel/time/tick-oneshot.c
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   1/*
   2 * linux/kernel/time/tick-oneshot.c
   3 *
   4 * This file contains functions which manage high resolution tick
   5 * related events.
   6 *
   7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
  10 *
  11 * This code is licenced under the GPL version 2. For details see
  12 * kernel-base/COPYING.
  13 */
  14#include <linux/cpu.h>
  15#include <linux/err.h>
  16#include <linux/hrtimer.h>
  17#include <linux/interrupt.h>
  18#include <linux/percpu.h>
  19#include <linux/profile.h>
  20#include <linux/sched.h>
  21
  22#include "tick-internal.h"
  23
  24/**
  25 * tick_program_event
  26 */
  27int tick_program_event(ktime_t expires, int force)
  28{
  29        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  30
  31        return clockevents_program_event(dev, expires, force);
  32}
  33
  34/**
  35 * tick_resume_onshot - resume oneshot mode
  36 */
  37void tick_resume_oneshot(void)
  38{
  39        struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  40
  41        clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  42        clockevents_program_event(dev, ktime_get(), true);
  43}
  44
  45/**
  46 * tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
  47 */
  48void tick_setup_oneshot(struct clock_event_device *newdev,
  49                        void (*handler)(struct clock_event_device *),
  50                        ktime_t next_event)
  51{
  52        newdev->event_handler = handler;
  53        clockevents_set_mode(newdev, CLOCK_EVT_MODE_ONESHOT);
  54        clockevents_program_event(newdev, next_event, true);
  55}
  56
  57/**
  58 * tick_switch_to_oneshot - switch to oneshot mode
  59 */
  60int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
  61{
  62        struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  63        struct clock_event_device *dev = td->evtdev;
  64
  65        if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
  66                    !tick_device_is_functional(dev)) {
  67
  68                printk(KERN_INFO "Clockevents: "
  69                       "could not switch to one-shot mode:");
  70                if (!dev) {
  71                        printk(" no tick device\n");
  72                } else {
  73                        if (!tick_device_is_functional(dev))
  74                                printk(" %s is not functional.\n", dev->name);
  75                        else
  76                                printk(" %s does not support one-shot mode.\n",
  77                                       dev->name);
  78                }
  79                return -EINVAL;
  80        }
  81
  82        td->mode = TICKDEV_MODE_ONESHOT;
  83        dev->event_handler = handler;
  84        clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  85        tick_broadcast_switch_to_oneshot();
  86        return 0;
  87}
  88
  89/**
  90 * tick_check_oneshot_mode - check whether the system is in oneshot mode
  91 *
  92 * returns 1 when either nohz or highres are enabled. otherwise 0.
  93 */
  94int tick_oneshot_mode_active(void)
  95{
  96        unsigned long flags;
  97        int ret;
  98
  99        local_irq_save(flags);
 100        ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
 101        local_irq_restore(flags);
 102
 103        return ret;
 104}
 105
 106#ifdef CONFIG_HIGH_RES_TIMERS
 107/**
 108 * tick_init_highres - switch to high resolution mode
 109 *
 110 * Called with interrupts disabled.
 111 */
 112int tick_init_highres(void)
 113{
 114        return tick_switch_to_oneshot(hrtimer_interrupt);
 115}
 116#endif
 117
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