- 根目录:
- 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 "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)
{
struct clock_event_device *cur = tick_broadcast_device.evtdev;
if ((dev->features & CLOCK_EVT_FEAT_DUMMY) ||
(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);
if (cur)
cur->event_handler = clockevents_handle_noop;
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);
/*
* 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_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;
}
}
/**
* 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(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