tick: Provide a check for a forced broadcast pending

[deliverable/linux.git] / kernel / time / tick-broadcast.c

/*
 * 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 <tglx@linutronix.de>
 * 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 <linux/smp.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;
static cpumask_var_t tick_broadcast_mask;
static cpumask_var_t tmpmask;
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 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_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);
}

static void err_broadcast(const struct cpumask *mask)
{
        pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
}

static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
{
        if (!dev->broadcast)
                dev->broadcast = tick_broadcast;
        if (!dev->broadcast) {
                pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
                             dev->name);
                dev->broadcast = err_broadcast;
        }
}

/*
 * 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;
                tick_device_setup_broadcast_func(dev);
                cpumask_set_cpu(cpu, tick_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_broadcast_mask);
                        tick_broadcast_clear_oneshot(cpu);
                } else {
                        tick_device_setup_broadcast_func(dev);
                }
        }
        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
        return ret;
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
int tick_receive_broadcast(void)
{
        struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
        struct clock_event_device *evt = td->evtdev;

        if (!evt)
                return -ENODEV;

        if (!evt->event_handler)
                return -EINVAL;

        evt->event_handler(evt);
        return 0;
}
#endif

/*
 * 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(tmpmask, cpu_online_mask, tick_broadcast_mask);
        tick_do_broadcast(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_broadcast_mask);

        switch (*reason) {
        case CLOCK_EVT_NOTIFY_BROADCAST_ON:
        case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
                if (!cpumask_test_and_set_cpu(cpu, tick_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_and_clear_cpu(cpu, tick_broadcast_mask)) {
                        if (tick_broadcast_device.mode ==
                            TICKDEV_MODE_PERIODIC)
                                tick_setup_periodic(dev, 0);
                }
                break;
        }

        if (cpumask_empty(tick_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_broadcast_mask);

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

        return broadcast;
}


#ifdef CONFIG_TICK_ONESHOT

static cpumask_var_t tick_broadcast_oneshot_mask;
static cpumask_var_t tick_broadcast_pending_mask;
static cpumask_var_t tick_broadcast_force_mask;

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

/*
 * Called before going idle with interrupts disabled. Checks whether a
 * broadcast event from the other core is about to happen. We detected
 * that in tick_broadcast_oneshot_control(). The callsite can use this
 * to avoid a deep idle transition as we are about to get the
 * broadcast IPI right away.
 */
int tick_check_broadcast_expired(void)
{
        return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
}

/*
 * Set broadcast interrupt affinity
 */
static void tick_broadcast_set_affinity(struct clock_event_device *bc,
                                        const struct cpumask *cpumask)
{
        if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
                return;

        if (cpumask_equal(bc->cpumask, cpumask))
                return;

        bc->cpumask = cpumask;
        irq_set_affinity(bc->irq, bc->cpumask);
}

static int tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
                                    ktime_t expires, int force)
{
        int ret;

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

        ret = clockevents_program_event(bc, expires, force);
        if (!ret)
                tick_broadcast_set_affinity(bc, cpumask_of(cpu));
        return ret;
}

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, 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, next_cpu = 0;

        raw_spin_lock(&tick_broadcast_lock);
again:
        dev->next_event.tv64 = KTIME_MAX;
        next_event.tv64 = KTIME_MAX;
        cpumask_clear(tmpmask);
        now = ktime_get();
        /* Find all expired events */
        for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
                td = &per_cpu(tick_cpu_device, cpu);
                if (td->evtdev->next_event.tv64 <= now.tv64) {
                        cpumask_set_cpu(cpu, tmpmask);
                        /*
                         * Mark the remote cpu in the pending mask, so
                         * it can avoid reprogramming the cpu local
                         * timer in tick_broadcast_oneshot_control().
                         */
                        cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
                } else if (td->evtdev->next_event.tv64 < next_event.tv64) {
                        next_event.tv64 = td->evtdev->next_event.tv64;
                        next_cpu = cpu;
                }
        }

        /* Take care of enforced broadcast requests */
        cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
        cpumask_clear(tick_broadcast_force_mask);

        /*
         * Wakeup the cpus which have an expired event.
         */
        tick_do_broadcast(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(dev, next_cpu, 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;
        ktime_t now;
        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) {
                WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
                if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
                        clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
                        /*
                         * We only reprogram the broadcast timer if we
                         * did not mark ourself in the force mask and
                         * if the cpu local event is earlier than the
                         * broadcast event. If the current CPU is in
                         * the force mask, then we are going to be
                         * woken by the IPI right away.
                         */
                        if (!cpumask_test_cpu(cpu, tick_broadcast_force_mask) &&
                            dev->next_event.tv64 < bc->next_event.tv64)
                                tick_broadcast_set_event(bc, cpu, dev->next_event, 1);
                }
        } else {
                if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
                        clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
                        if (dev->next_event.tv64 == KTIME_MAX)
                                goto out;
                        /*
                         * The cpu which was handling the broadcast
                         * timer marked this cpu in the broadcast
                         * pending mask and fired the broadcast
                         * IPI. So we are going to handle the expired
                         * event anyway via the broadcast IPI
                         * handler. No need to reprogram the timer
                         * with an already expired event.
                         */
                        if (cpumask_test_and_clear_cpu(cpu,
                                       tick_broadcast_pending_mask))
                                goto out;

                        /*
                         * If the pending bit is not set, then we are
                         * either the CPU handling the broadcast
                         * interrupt or we got woken by something else.
                         *
                         * We are not longer in the broadcast mask, so
                         * if the cpu local expiry time is already
                         * reached, we would reprogram the cpu local
                         * timer with an already expired event.
                         *
                         * This can lead to a ping-pong when we return
                         * to idle and therefor rearm the broadcast
                         * timer before the cpu local timer was able
                         * to fire. This happens because the forced
                         * reprogramming makes sure that the event
                         * will happen in the future and depending on
                         * the min_delta setting this might be far
                         * enough out that the ping-pong starts.
                         *
                         * If the cpu local next_event has expired
                         * then we know that the broadcast timer
                         * next_event has expired as well and
                         * broadcast is about to be handled. So we
                         * avoid reprogramming and enforce that the
                         * broadcast handler, which did not run yet,
                         * will invoke the cpu local handler.
                         *
                         * We cannot call the handler directly from
                         * here, because we might be in a NOHZ phase
                         * and we did not go through the irq_enter()
                         * nohz fixups.
                         */
                        now = ktime_get();
                        if (dev->next_event.tv64 <= now.tv64) {
                                cpumask_set_cpu(cpu, tick_broadcast_force_mask);
                                goto out;
                        }
                        /*
                         * We got woken by something else. Reprogram
                         * the cpu local timer device.
                         */
                        tick_program_event(dev->next_event, 1);
                }
        }
out:
        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_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;
        }
}

/**
 * tick_broadcast_setup_oneshot - setup the broadcast device
 */
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(tmpmask, tick_broadcast_mask);
                cpumask_clear_cpu(cpu, tmpmask);
                cpumask_or(tick_broadcast_oneshot_mask,
                           tick_broadcast_oneshot_mask, tmpmask);

                if (was_periodic && !cpumask_empty(tmpmask)) {
                        clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
                        tick_broadcast_init_next_event(tmpmask,
                                                       tick_next_period);
                        tick_broadcast_set_event(bc, cpu, 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_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

void __init tick_broadcast_init(void)
{
        alloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
        alloc_cpumask_var(&tmpmask, GFP_NOWAIT);
#ifdef CONFIG_TICK_ONESHOT
        alloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
        alloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
        alloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
#endif
}