/*
* Setup the device for a periodic tick
*/
void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
{
tick_set_periodic_handler(dev, broadcast);
/* Broadcast setup ? */
if (!tick_device_is_functional(dev))
return;
if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
!tick_broadcast_oneshot_active()) {
clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
} else {
unsigned long seq;
ktime_t next;
do {
seq = read_seqbegin(&jiffies_lock);
next = tick_next_period;
} while (read_seqretry(&jiffies_lock, seq));
clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
for (;;) {
if (!clockevents_program_event(dev, next, false))
return;
next = ktime_add(next, tick_period);
}
}
}
static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
ktime_t expires)
{
if (!clockevent_state_oneshot(bc))
clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
clockevents_program_event(bc, expires, 1);
tick_broadcast_set_affinity(bc, cpumask_of(cpu));
}
static void broadcast_shutdown_local(struct clock_event_device *bc,
struct clock_event_device *dev)
{
/*
* For hrtimer based broadcasting we cannot shutdown the cpu
* local device if our own event is the first one to expire or
* if we own the broadcast timer.
*/
if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
if (broadcast_needs_cpu(bc, smp_processor_id()))
return;
if (dev->next_event < bc->next_event)
return;
}
clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
}
/*
* Called from irq_enter() when idle was interrupted to reenable the
* per cpu device.
*/
void tick_check_oneshot_broadcast_this_cpu(void)
{
if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
/*
* We might be in the middle of switching over from
* periodic to oneshot. If the CPU has not yet
* switched over, leave the device alone.
*/
if (td->mode == TICKDEV_MODE_ONESHOT) {
clockevents_switch_state(td->evtdev,
CLOCK_EVT_STATE_ONESHOT);
}
}
}
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
{
struct clock_event_device *bc, *dev;
int cpu, ret = 0;
ktime_t now;
/*
* If there is no broadcast device, tell the caller not to go
* into deep idle.
*/
if (!tick_broadcast_device.evtdev)
return -EBUSY;
dev = this_cpu_ptr(&tick_cpu_device)->evtdev;
raw_spin_lock(&tick_broadcast_lock);
bc = tick_broadcast_device.evtdev;
cpu = smp_processor_id();
if (state == TICK_BROADCAST_ENTER) {
/*
* If the current CPU owns the hrtimer broadcast
* mechanism, it cannot go deep idle and we do not add
* the CPU to the broadcast mask. We don't have to go
* through the EXIT path as the local timer is not
* shutdown.
*/
ret = broadcast_needs_cpu(bc, cpu);
if (ret)
goto out;
/*
* If the broadcast device is in periodic mode, we
* return.
*/
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
/* If it is a hrtimer based broadcast, return busy */
if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
ret = -EBUSY;
goto out;
}
if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
/* Conditionally shut down the local timer. */
broadcast_shutdown_local(bc, dev);
/*
* 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; we return
* busy, so the CPU does not try to go deep
* idle.
*/
if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
ret = -EBUSY;
} else if (dev->next_event < bc->next_event) {
tick_broadcast_set_event(bc, cpu, dev->next_event);
/*
* In case of hrtimer broadcasts the
* programming might have moved the
* timer to this cpu. If yes, remove
* us from the broadcast mask and
* return busy.
*/
ret = broadcast_needs_cpu(bc, cpu);
if (ret) {
cpumask_clear_cpu(cpu,
tick_broadcast_oneshot_mask);
}
}
}
} else {
if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
/*
* 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;
/*
* Bail out if there is no next event.
*/
if (dev->next_event == KTIME_MAX)
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 <= now) {
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(&tick_broadcast_lock);
return ret;
}
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
{
clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
}
