tick-broadcast.c

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/*
 * linux/kernel/time/tick-broadcast.c
 *
 * This file contains functions which emulate a local clock-event
 * device via a broadcast event source.
 *
 * Copyright(C) 2005-2006, Thomas Gleixner <[email protected]>
 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
 *
 * This code is licenced under the GPL version 2. For details see
 * kernel-base/COPYING.
 */
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>

#include "tick-internal.h"

/*
 * Broadcast support for broken x86 hardware, where the local apic
 * timer stops in C3 state.
 */

static struct tick_device tick_broadcast_device;
/* FIXME: Use cpumask_var_t. */
static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
static DECLARE_BITMAP(tmpmask, NR_CPUS);
static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
static int tick_broadcast_force;

#ifdef CONFIG_TICK_ONESHOT
static void tick_broadcast_clear_oneshot(int cpu);
#else
static inline void tick_broadcast_clear_oneshot(int cpu) { }
#endif

/*
 * Debugging: see timer_list.c
 */
struct tick_device *tick_get_broadcast_device(void)
{
    return &tick_broadcast_device;
}

struct cpumask *tick_get_broadcast_mask(void)
{
    return to_cpumask(tick_broadcast_mask);
}

/*
 * Start the device in periodic mode
 */
static void tick_broadcast_start_periodic(struct clock_event_device *bc)
{
    if (bc)
        tick_setup_periodic(bc, 1);
}

/*
 * Check, if the device can be utilized as broadcast device:
 */
int tick_check_broadcast_device(struct clock_event_device *dev)
{
    if ((tick_broadcast_device.evtdev &&
         tick_broadcast_device.evtdev->rating >= dev->rating) ||
         (dev->features & CLOCK_EVT_FEAT_C3STOP))
        return 0;

    clockevents_exchange_device(tick_broadcast_device.evtdev, dev);
    tick_broadcast_device.evtdev = dev;
    if (!cpumask_empty(tick_get_broadcast_mask()))
        tick_broadcast_start_periodic(dev);
    return 1;
}

/*
 * Check, if the device is the broadcast device
 */
int tick_is_broadcast_device(struct clock_event_device *dev)
{
    return (dev && tick_broadcast_device.evtdev == dev);
}

/*
 * Check, if the device is disfunctional and a place holder, which
 * needs to be handled by the broadcast device.
 */
int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
{
    unsigned long flags;
    int ret = 0;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    /*
     * Devices might be registered with both periodic and oneshot
     * mode disabled. This signals, that the device needs to be
     * operated from the broadcast device and is a placeholder for
     * the cpu local device.
     */
    if (!tick_device_is_functional(dev)) {
        dev->event_handler = tick_handle_periodic;
        cpumask_set_cpu(cpu, tick_get_broadcast_mask());
        tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
        ret = 1;
    } else {
        /*
         * When the new device is not affected by the stop
         * feature and the cpu is marked in the broadcast mask
         * then clear the broadcast bit.
         */
        if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
            int cpu = smp_processor_id();

            cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
            tick_broadcast_clear_oneshot(cpu);
        }
    }
    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
    return ret;
}

/*
 * Broadcast the event to the cpus, which are set in the mask (mangled).
 */
static void tick_do_broadcast(struct cpumask *mask)
{
    int cpu = smp_processor_id();
    struct tick_device *td;

    /*
     * Check, if the current cpu is in the mask
     */
    if (cpumask_test_cpu(cpu, mask)) {
        cpumask_clear_cpu(cpu, mask);
        td = &per_cpu(tick_cpu_device, cpu);
        td->evtdev->event_handler(td->evtdev);
    }

    if (!cpumask_empty(mask)) {
        /*
         * It might be necessary to actually check whether the devices
         * have different broadcast functions. For now, just use the
         * one of the first device. This works as long as we have this
         * misfeature only on x86 (lapic)
         */
        td = &per_cpu(tick_cpu_device, cpumask_first(mask));
        td->evtdev->broadcast(mask);
    }
}

/*
 * Periodic broadcast:
 * - invoke the broadcast handlers
 */
static void tick_do_periodic_broadcast(void)
{
    raw_spin_lock(&tick_broadcast_lock);

    cpumask_and(to_cpumask(tmpmask),
            cpu_online_mask, tick_get_broadcast_mask());
    tick_do_broadcast(to_cpumask(tmpmask));

    raw_spin_unlock(&tick_broadcast_lock);
}

/*
 * Event handler for periodic broadcast ticks
 */
static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
{
    ktime_t next;

    tick_do_periodic_broadcast();

    /*
     * The device is in periodic mode. No reprogramming necessary:
     */
    if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
        return;

    /*
     * Setup the next period for devices, which do not have
     * periodic mode. We read dev->next_event first and add to it
     * when the event already expired. clockevents_program_event()
     * sets dev->next_event only when the event is really
     * programmed to the device.
     */
    for (next = dev->next_event; ;) {
        next = ktime_add(next, tick_period);

        if (!clockevents_program_event(dev, next, false))
            return;
        tick_do_periodic_broadcast();
    }
}

/*
 * Powerstate information: The system enters/leaves a state, where
 * affected devices might stop
 */
static void tick_do_broadcast_on_off(unsigned long *reason)
{
    struct clock_event_device *bc, *dev;
    struct tick_device *td;
    unsigned long flags;
    int cpu, bc_stopped;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    cpu = smp_processor_id();
    td = &per_cpu(tick_cpu_device, cpu);
    dev = td->evtdev;
    bc = tick_broadcast_device.evtdev;

    /*
     * Is the device not affected by the powerstate ?
     */
    if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
        goto out;

    if (!tick_device_is_functional(dev))
        goto out;

    bc_stopped = cpumask_empty(tick_get_broadcast_mask());

    switch (*reason) {
    case CLOCK_EVT_NOTIFY_BROADCAST_ON:
    case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
        if (!cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
            cpumask_set_cpu(cpu, tick_get_broadcast_mask());
            if (tick_broadcast_device.mode ==
                TICKDEV_MODE_PERIODIC)
                clockevents_shutdown(dev);
        }
        if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
            tick_broadcast_force = 1;
        break;
    case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
        if (!tick_broadcast_force &&
            cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
            cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
            if (tick_broadcast_device.mode ==
                TICKDEV_MODE_PERIODIC)
                tick_setup_periodic(dev, 0);
        }
        break;
    }

    if (cpumask_empty(tick_get_broadcast_mask())) {
        if (!bc_stopped)
            clockevents_shutdown(bc);
    } else if (bc_stopped) {
        if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
            tick_broadcast_start_periodic(bc);
        else
            tick_broadcast_setup_oneshot(bc);
    }
out:
    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

/*
 * Powerstate information: The system enters/leaves a state, where
 * affected devices might stop.
 */
void tick_broadcast_on_off(unsigned long reason, int *oncpu)
{
    if (!cpumask_test_cpu(*oncpu, cpu_online_mask))
        printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
               "offline CPU #%d\n", *oncpu);
    else
        tick_do_broadcast_on_off(&reason);
}

/*
 * Set the periodic handler depending on broadcast on/off
 */
void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
{
    if (!broadcast)
        dev->event_handler = tick_handle_periodic;
    else
        dev->event_handler = tick_handle_periodic_broadcast;
}

/*
 * Remove a CPU from broadcasting
 */
void tick_shutdown_broadcast(unsigned int *cpup)
{
    struct clock_event_device *bc;
    unsigned long flags;
    unsigned int cpu = *cpup;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    bc = tick_broadcast_device.evtdev;
    cpumask_clear_cpu(cpu, tick_get_broadcast_mask());

    if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
        if (bc && cpumask_empty(tick_get_broadcast_mask()))
            clockevents_shutdown(bc);
    }

    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

void tick_suspend_broadcast(void)
{
    struct clock_event_device *bc;
    unsigned long flags;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    bc = tick_broadcast_device.evtdev;
    if (bc)
        clockevents_shutdown(bc);

    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

int tick_resume_broadcast(void)
{
    struct clock_event_device *bc;
    unsigned long flags;
    int broadcast = 0;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    bc = tick_broadcast_device.evtdev;

    if (bc) {
        clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);

        switch (tick_broadcast_device.mode) {
        case TICKDEV_MODE_PERIODIC:
            if (!cpumask_empty(tick_get_broadcast_mask()))
                tick_broadcast_start_periodic(bc);
            broadcast = cpumask_test_cpu(smp_processor_id(),
                             tick_get_broadcast_mask());
            break;
        case TICKDEV_MODE_ONESHOT:
            if (!cpumask_empty(tick_get_broadcast_mask()))
                broadcast = tick_resume_broadcast_oneshot(bc);
            break;
        }
    }
    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

    return broadcast;
}


#ifdef CONFIG_TICK_ONESHOT

/* FIXME: use cpumask_var_t. */
static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);

/*
 * Exposed for debugging: see timer_list.c
 */
struct cpumask *tick_get_broadcast_oneshot_mask(void)
{
    return to_cpumask(tick_broadcast_oneshot_mask);
}

static int tick_broadcast_set_event(ktime_t expires, int force)
{
    struct clock_event_device *bc = tick_broadcast_device.evtdev;

    if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
        clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);

    return clockevents_program_event(bc, expires, force);
}

int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
{
    clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
    return 0;
}

/*
 * Called from irq_enter() when idle was interrupted to reenable the
 * per cpu device.
 */
void tick_check_oneshot_broadcast(int cpu)
{
    if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) {
        struct tick_device *td = &per_cpu(tick_cpu_device, cpu);

        clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
    }
}

/*
 * Handle oneshot mode broadcasting
 */
static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
{
    struct tick_device *td;
    ktime_t now, next_event;
    int cpu;

    raw_spin_lock(&tick_broadcast_lock);
again:
    dev->next_event.tv64 = KTIME_MAX;
    next_event.tv64 = KTIME_MAX;
    cpumask_clear(to_cpumask(tmpmask));
    now = ktime_get();
    /* Find all expired events */
    for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) {
        td = &per_cpu(tick_cpu_device, cpu);
        if (td->evtdev->next_event.tv64 <= now.tv64)
            cpumask_set_cpu(cpu, to_cpumask(tmpmask));
        else if (td->evtdev->next_event.tv64 < next_event.tv64)
            next_event.tv64 = td->evtdev->next_event.tv64;
    }

    /*
     * Wakeup the cpus which have an expired event.
     */
    tick_do_broadcast(to_cpumask(tmpmask));

    /*
     * Two reasons for reprogram:
     *
     * - The global event did not expire any CPU local
     * events. This happens in dyntick mode, as the maximum PIT
     * delta is quite small.
     *
     * - There are pending events on sleeping CPUs which were not
     * in the event mask
     */
    if (next_event.tv64 != KTIME_MAX) {
        /*
         * Rearm the broadcast device. If event expired,
         * repeat the above
         */
        if (tick_broadcast_set_event(next_event, 0))
            goto again;
    }
    raw_spin_unlock(&tick_broadcast_lock);
}

/*
 * Powerstate information: The system enters/leaves a state, where
 * affected devices might stop
 */
void tick_broadcast_oneshot_control(unsigned long reason)
{
    struct clock_event_device *bc, *dev;
    struct tick_device *td;
    unsigned long flags;
    int cpu;

    /*
     * Periodic mode does not care about the enter/exit of power
     * states
     */
    if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
        return;

    /*
     * We are called with preemtion disabled from the depth of the
     * idle code, so we can't be moved away.
     */
    cpu = smp_processor_id();
    td = &per_cpu(tick_cpu_device, cpu);
    dev = td->evtdev;

    if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
        return;

    bc = tick_broadcast_device.evtdev;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
    if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
        if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
            cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
            clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
            if (dev->next_event.tv64 < bc->next_event.tv64)
                tick_broadcast_set_event(dev->next_event, 1);
        }
    } else {
        if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
            cpumask_clear_cpu(cpu,
                      tick_get_broadcast_oneshot_mask());
            clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
            if (dev->next_event.tv64 != KTIME_MAX)
                tick_program_event(dev->next_event, 1);
        }
    }
    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

/*
 * Reset the one shot broadcast for a cpu
 *
 * Called with tick_broadcast_lock held
 */
static void tick_broadcast_clear_oneshot(int cpu)
{
    cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
}

static void tick_broadcast_init_next_event(struct cpumask *mask,
                       ktime_t expires)
{
    struct tick_device *td;
    int cpu;

    for_each_cpu(cpu, mask) {
        td = &per_cpu(tick_cpu_device, cpu);
        if (td->evtdev)
            td->evtdev->next_event = expires;
    }
}

void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
{
    int cpu = smp_processor_id();

    /* Set it up only once ! */
    if (bc->event_handler != tick_handle_oneshot_broadcast) {
        int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;

        bc->event_handler = tick_handle_oneshot_broadcast;

        /* Take the do_timer update */
        tick_do_timer_cpu = cpu;

        /*
         * We must be careful here. There might be other CPUs
         * waiting for periodic broadcast. We need to set the
         * oneshot_mask bits for those and program the
         * broadcast device to fire.
         */
        cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask());
        cpumask_clear_cpu(cpu, to_cpumask(tmpmask));
        cpumask_or(tick_get_broadcast_oneshot_mask(),
               tick_get_broadcast_oneshot_mask(),
               to_cpumask(tmpmask));

        if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
            clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
            tick_broadcast_init_next_event(to_cpumask(tmpmask),
                               tick_next_period);
            tick_broadcast_set_event(tick_next_period, 1);
        } else
            bc->next_event.tv64 = KTIME_MAX;
    } else {
        /*
         * The first cpu which switches to oneshot mode sets
         * the bit for all other cpus which are in the general
         * (periodic) broadcast mask. So the bit is set and
         * would prevent the first broadcast enter after this
         * to program the bc device.
         */
        tick_broadcast_clear_oneshot(cpu);
    }
}

/*
 * Select oneshot operating mode for the broadcast device
 */
void tick_broadcast_switch_to_oneshot(void)
{
    struct clock_event_device *bc;
    unsigned long flags;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
    bc = tick_broadcast_device.evtdev;
    if (bc)
        tick_broadcast_setup_oneshot(bc);

    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}


/*
 * Remove a dead CPU from broadcasting
 */
void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
{
    unsigned long flags;
    unsigned int cpu = *cpup;

    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    /*
     * Clear the broadcast mask flag for the dead cpu, but do not
     * stop the broadcast device!
     */
    cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());

    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}

/*
 * Check, whether the broadcast device is in one shot mode
 */
int tick_broadcast_oneshot_active(void)
{
    return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
}

/*
 * Check whether the broadcast device supports oneshot.
 */
bool tick_broadcast_oneshot_available(void)
{
    struct clock_event_device *bc = tick_broadcast_device.evtdev;

    return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
}

#endif