f8381cba04
With Ingo Molnar <mingo@elte.hu> Add broadcast functionality, so per cpu clock event devices can be registered as dummy devices or switched from/to broadcast on demand. The broadcast function distributes the events via the broadcast function of the clock event device. This is primarily designed to replace the switch apic timer to / from IPI in power states, where the apic stops. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
271 lines
6.4 KiB
C
271 lines
6.4 KiB
C
/*
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* linux/kernel/time/tick-broadcast.c
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*
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* This file contains functions which emulate a local clock-event
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* device via a broadcast event source.
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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/irq.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 <linux/tick.h>
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#include "tick-internal.h"
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/*
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* Broadcast support for broken x86 hardware, where the local apic
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* timer stops in C3 state.
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*/
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struct tick_device tick_broadcast_device;
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static cpumask_t tick_broadcast_mask;
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DEFINE_SPINLOCK(tick_broadcast_lock);
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/*
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* Start the device in periodic mode
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*/
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static void tick_broadcast_start_periodic(struct clock_event_device *bc)
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{
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if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
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tick_setup_periodic(bc, 1);
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}
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/*
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* Check, if the device can be utilized as broadcast device:
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*/
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int tick_check_broadcast_device(struct clock_event_device *dev)
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{
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if (tick_broadcast_device.evtdev ||
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(dev->features & CLOCK_EVT_FEAT_C3STOP))
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return 0;
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clockevents_exchange_device(NULL, dev);
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tick_broadcast_device.evtdev = dev;
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if (!cpus_empty(tick_broadcast_mask))
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tick_broadcast_start_periodic(dev);
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return 1;
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}
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/*
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* Check, if the device is the broadcast device
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*/
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int tick_is_broadcast_device(struct clock_event_device *dev)
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{
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return (dev && tick_broadcast_device.evtdev == dev);
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}
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/*
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* Check, if the device is disfunctional and a place holder, which
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* needs to be handled by the broadcast device.
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*/
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int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
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{
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unsigned long flags;
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int ret = 0;
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spin_lock_irqsave(&tick_broadcast_lock, flags);
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/*
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* Devices might be registered with both periodic and oneshot
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* mode disabled. This signals, that the device needs to be
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* operated from the broadcast device and is a placeholder for
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* the cpu local device.
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*/
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if (!tick_device_is_functional(dev)) {
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dev->event_handler = tick_handle_periodic;
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cpu_set(cpu, tick_broadcast_mask);
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tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
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ret = 1;
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}
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spin_unlock_irqrestore(&tick_broadcast_lock, flags);
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return ret;
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}
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/*
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* Broadcast the event to the cpus, which are set in the mask
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*/
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int tick_do_broadcast(cpumask_t mask)
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{
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int ret = 0, cpu = smp_processor_id();
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struct tick_device *td;
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/*
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* Check, if the current cpu is in the mask
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*/
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if (cpu_isset(cpu, mask)) {
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cpu_clear(cpu, mask);
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td = &per_cpu(tick_cpu_device, cpu);
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td->evtdev->event_handler(td->evtdev);
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ret = 1;
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}
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if (!cpus_empty(mask)) {
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/*
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* It might be necessary to actually check whether the devices
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* have different broadcast functions. For now, just use the
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* one of the first device. This works as long as we have this
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* misfeature only on x86 (lapic)
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*/
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cpu = first_cpu(mask);
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td = &per_cpu(tick_cpu_device, cpu);
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td->evtdev->broadcast(mask);
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ret = 1;
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}
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return ret;
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}
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/*
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* Periodic broadcast:
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* - invoke the broadcast handlers
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*/
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static void tick_do_periodic_broadcast(void)
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{
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cpumask_t mask;
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spin_lock(&tick_broadcast_lock);
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cpus_and(mask, cpu_online_map, tick_broadcast_mask);
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tick_do_broadcast(mask);
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spin_unlock(&tick_broadcast_lock);
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}
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/*
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* Event handler for periodic broadcast ticks
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*/
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static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
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{
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dev->next_event.tv64 = KTIME_MAX;
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tick_do_periodic_broadcast();
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/*
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* The device is in periodic mode. No reprogramming necessary:
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*/
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if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
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return;
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/*
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* Setup the next period for devices, which do not have
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* periodic mode:
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*/
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for (;;) {
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ktime_t next = ktime_add(dev->next_event, tick_period);
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if (!clockevents_program_event(dev, next, ktime_get()))
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return;
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tick_do_periodic_broadcast();
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}
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}
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/*
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* Powerstate information: The system enters/leaves a state, where
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* affected devices might stop
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*/
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static void tick_do_broadcast_on_off(void *why)
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{
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struct clock_event_device *bc, *dev;
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struct tick_device *td;
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unsigned long flags, *reason = why;
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int cpu;
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spin_lock_irqsave(&tick_broadcast_lock, flags);
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cpu = smp_processor_id();
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td = &per_cpu(tick_cpu_device, cpu);
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dev = td->evtdev;
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bc = tick_broadcast_device.evtdev;
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/*
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* Is the device in broadcast mode forever or is it not
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* affected by the powerstate ?
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*/
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if (!dev || !tick_device_is_functional(dev) ||
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!(dev->features & CLOCK_EVT_FEAT_C3STOP))
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goto out;
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if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
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if (!cpu_isset(cpu, tick_broadcast_mask)) {
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cpu_set(cpu, tick_broadcast_mask);
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if (td->mode == TICKDEV_MODE_PERIODIC)
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clockevents_set_mode(dev,
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CLOCK_EVT_MODE_SHUTDOWN);
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}
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} else {
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if (cpu_isset(cpu, tick_broadcast_mask)) {
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cpu_clear(cpu, tick_broadcast_mask);
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if (td->mode == TICKDEV_MODE_PERIODIC)
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tick_setup_periodic(dev, 0);
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}
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}
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if (cpus_empty(tick_broadcast_mask))
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clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
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else {
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if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
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tick_broadcast_start_periodic(bc);
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}
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out:
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spin_unlock_irqrestore(&tick_broadcast_lock, flags);
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}
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/*
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* Powerstate information: The system enters/leaves a state, where
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* affected devices might stop.
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*/
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void tick_broadcast_on_off(unsigned long reason, int *oncpu)
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{
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int cpu = get_cpu();
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if (cpu == *oncpu)
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tick_do_broadcast_on_off(&reason);
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else
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smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
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&reason, 1, 1);
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put_cpu();
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}
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/*
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* Set the periodic handler depending on broadcast on/off
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*/
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void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
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{
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if (!broadcast)
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dev->event_handler = tick_handle_periodic;
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else
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dev->event_handler = tick_handle_periodic_broadcast;
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}
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/*
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* Remove a CPU from broadcasting
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*/
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void tick_shutdown_broadcast(unsigned int *cpup)
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{
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struct clock_event_device *bc;
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unsigned long flags;
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unsigned int cpu = *cpup;
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spin_lock_irqsave(&tick_broadcast_lock, flags);
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bc = tick_broadcast_device.evtdev;
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cpu_clear(cpu, tick_broadcast_mask);
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if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
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if (bc && cpus_empty(tick_broadcast_mask))
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clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
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}
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spin_unlock_irqrestore(&tick_broadcast_lock, flags);
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}
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