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clockevent_device::next_event holds the next timer event of a clock event device. The value is updated in clockevents_program_event(), i.e. when the hardware timer is armed for the next expiry. When there are no software timers armed on a CPU, the corresponding per CPU clockevent device is brought into ONESHOT_STOPPED state, but clockevent_device::next_event is not updated, because clockevents_program_event() is not called. So the content of clockevent_device::next_event is stale, which is not an issue when real hardware is used. But the hrtimer broadcast device relies on that information and the stale value causes spurious wakeups. Update clockevent_device::next_event to KTIME_MAX when it has been brought into ONESHOT_STOPPED state to avoid spurious wakeups. This reflects the proper expiry time of the stopped timer: infinity. [ tglx: Massaged changelog ] Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: viresh.kumar@linaro.org Link: https://lkml.kernel.org/r/1509043042-32486-1-git-send-email-psodagud@codeaurora.org
134 lines
3.3 KiB
C
134 lines
3.3 KiB
C
/*
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* linux/kernel/time/tick-oneshot.c
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*
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* This file contains functions which manage high resolution 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/interrupt.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 "tick-internal.h"
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/**
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* tick_program_event
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*/
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int tick_program_event(ktime_t expires, int force)
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{
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struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
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if (unlikely(expires == KTIME_MAX)) {
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/*
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* We don't need the clock event device any more, stop it.
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*/
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clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
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dev->next_event = KTIME_MAX;
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return 0;
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}
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if (unlikely(clockevent_state_oneshot_stopped(dev))) {
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/*
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* We need the clock event again, configure it in ONESHOT mode
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* before using it.
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*/
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clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
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}
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return clockevents_program_event(dev, expires, force);
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}
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/**
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* tick_resume_onshot - resume oneshot mode
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*/
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void tick_resume_oneshot(void)
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{
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struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
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clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
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clockevents_program_event(dev, ktime_get(), true);
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}
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/**
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* tick_setup_oneshot - setup the event device for oneshot mode (hres or nohz)
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*/
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void tick_setup_oneshot(struct clock_event_device *newdev,
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void (*handler)(struct clock_event_device *),
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ktime_t next_event)
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{
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newdev->event_handler = handler;
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clockevents_switch_state(newdev, CLOCK_EVT_STATE_ONESHOT);
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clockevents_program_event(newdev, next_event, true);
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}
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/**
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* tick_switch_to_oneshot - switch to oneshot mode
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*/
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int tick_switch_to_oneshot(void (*handler)(struct clock_event_device *))
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{
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struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
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struct clock_event_device *dev = td->evtdev;
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if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT) ||
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!tick_device_is_functional(dev)) {
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printk(KERN_INFO "Clockevents: "
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"could not switch to one-shot mode:");
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if (!dev) {
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printk(" no tick device\n");
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} else {
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if (!tick_device_is_functional(dev))
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printk(" %s is not functional.\n", dev->name);
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else
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printk(" %s does not support one-shot mode.\n",
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dev->name);
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}
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return -EINVAL;
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}
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td->mode = TICKDEV_MODE_ONESHOT;
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dev->event_handler = handler;
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clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
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tick_broadcast_switch_to_oneshot();
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return 0;
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}
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/**
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* tick_check_oneshot_mode - check whether the system is in oneshot mode
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*
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* returns 1 when either nohz or highres are enabled. otherwise 0.
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*/
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int tick_oneshot_mode_active(void)
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{
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unsigned long flags;
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int ret;
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local_irq_save(flags);
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ret = __this_cpu_read(tick_cpu_device.mode) == TICKDEV_MODE_ONESHOT;
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local_irq_restore(flags);
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return ret;
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}
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#ifdef CONFIG_HIGH_RES_TIMERS
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/**
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* tick_init_highres - switch to high resolution mode
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*
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* Called with interrupts disabled.
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*/
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int tick_init_highres(void)
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{
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return tick_switch_to_oneshot(hrtimer_interrupt);
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}
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#endif
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