/*
* Check, if the new registered device should be used. Called with
* clockevents_lock held and interrupts disabled.
*/
void tick_check_new_device(struct clock_event_device *newdev)
{
struct clock_event_device *curdev;
struct tick_device *td;
int cpu;
cpu = smp_processor_id();
td = &per_cpu(tick_cpu_device, cpu);
curdev = td->evtdev;
/* cpu local device ? */
if (!tick_check_percpu(curdev, newdev, cpu))
goto out_bc;
/* Preference decision */
if (!tick_check_preferred(curdev, newdev))
goto out_bc;
if (!try_module_get(newdev->owner))
return;
/*
* Replace the eventually existing device by the new
* device. If the current device is the broadcast device, do
* not give it back to the clockevents layer !
*/
if (tick_is_broadcast_device(curdev)) {
clockevents_shutdown(curdev);
curdev = NULL;
}
clockevents_exchange_device(curdev, newdev);
tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
tick_oneshot_notify();
return;
out_bc:
/*
* Can the new device be used as a broadcast device ?
*/
tick_install_broadcast_device(newdev);
}
/**
* clockevents_exchange_device - release and request clock devices
* @old: device to release (can be NULL)
* @new: device to request (can be NULL)
*
* Called from various tick functions with clockevents_lock held and
* interrupts disabled.
*/
void clockevents_exchange_device(struct clock_event_device *old,
struct clock_event_device *new)
{
/*
* Caller releases a clock event device. We queue it into the
* released list and do a notify add later.
*/
if (old) {
module_put(old->owner);
clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
list_del(&old->list);
list_add(&old->list, &clockevents_released);
}
if (new) {
BUG_ON(!clockevent_state_detached(new));
clockevents_shutdown(new);
}
}
/*
* Setup the tick device
*/
static void tick_setup_device(struct tick_device *td,
struct clock_event_device *newdev, int cpu,
const struct cpumask *cpumask)
{
ktime_t next_event;
void (*handler)(struct clock_event_device *) = NULL;
/*
* First device setup ?
*/
if (!td->evtdev) {
/*
* If no cpu took the do_timer update, assign it to
* this cpu:
*/
if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
if (!tick_nohz_full_cpu(cpu))
tick_do_timer_cpu = cpu;
else
tick_do_timer_cpu = TICK_DO_TIMER_NONE;
tick_next_period = ktime_get();
tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
}
/*
* Startup in periodic mode first.
*/
td->mode = TICKDEV_MODE_PERIODIC;
} else {
handler = td->evtdev->event_handler;
next_event = td->evtdev->next_event;
td->evtdev->event_handler = clockevents_handle_noop;
}
td->evtdev = newdev;
/*
* When the device is not per cpu, pin the interrupt to the
* current cpu:
*/
if (!cpumask_equal(newdev->cpumask, cpumask))
irq_set_affinity(newdev->irq, cpumask);
/*
* When global broadcasting is active, check if the current
* device is registered as a placeholder for broadcast mode.
* This allows us to handle this x86 misfeature in a generic
* way. This function also returns !=0 when we keep the
* current active broadcast state for this CPU.
*/
if (tick_device_uses_broadcast(newdev, cpu))
return;
if (td->mode == TICKDEV_MODE_PERIODIC)
tick_setup_periodic(newdev, 0);
else
tick_setup_oneshot(newdev, handler, next_event);
}
Linux 内核时钟架构之时钟事件设备和tick_device绑定
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