Commit 906568c9 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
Browse files

[PATCH] tick-management: core functionality



With Ingo Molnar <mingo@elte.hu>

The tick-management code is the first user of the clockevents layer.  It takes
clock event devices from the clock events core and uses them to provide the
periodic tick.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d316c57f
/* linux/include/linux/tick.h
*
* This file contains the structure definitions for tick related functions
*
*/
#ifndef _LINUX_TICK_H
#define _LINUX_TICK_H
#include <linux/clockchips.h>
#ifdef CONFIG_GENERIC_CLOCKEVENTS
enum tick_device_mode {
TICKDEV_MODE_PERIODIC,
TICKDEV_MODE_ONESHOT,
};
struct tick_device {
struct clock_event_device *evtdev;
enum tick_device_mode mode;
};
extern void __init tick_init(void);
#else
static inline void tick_init(void) { }
#endif
#endif
......@@ -40,6 +40,7 @@
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/efi.h>
#include <linux/tick.h>
#include <linux/taskstats_kern.h>
#include <linux/delayacct.h>
#include <linux/unistd.h>
......@@ -515,6 +516,7 @@ asmlinkage void __init start_kernel(void)
* enable them
*/
lock_kernel();
tick_init();
boot_cpu_init();
page_address_init();
printk(KERN_NOTICE);
......
obj-y += ntp.o clocksource.o jiffies.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
/*
* linux/kernel/time/tick-common.c
*
* This file contains the base functions to manage periodic tick
* related events.
*
* 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/irq.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/tick.h>
/*
* Tick devices
*/
static DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
/*
* Tick next event: keeps track of the tick time
*/
static ktime_t tick_next_period;
static ktime_t tick_period;
static int tick_do_timer_cpu = -1;
static DEFINE_SPINLOCK(tick_device_lock);
/*
* Periodic tick
*/
static void tick_periodic(int cpu)
{
if (tick_do_timer_cpu == cpu) {
write_seqlock(&xtime_lock);
/* Keep track of the next tick event */
tick_next_period = ktime_add(tick_next_period, tick_period);
do_timer(1);
write_sequnlock(&xtime_lock);
}
update_process_times(user_mode(get_irq_regs()));
profile_tick(CPU_PROFILING);
}
/*
* Event handler for periodic ticks
*/
void tick_handle_periodic(struct clock_event_device *dev)
{
int cpu = smp_processor_id();
tick_periodic(cpu);
if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
return;
/*
* Setup the next period for devices, which do not have
* periodic mode:
*/
for (;;) {
ktime_t next = ktime_add(dev->next_event, tick_period);
if (!clockevents_program_event(dev, next, ktime_get()))
return;
tick_periodic(cpu);
}
}
/*
* Setup the device for a periodic tick
*/
void tick_setup_periodic(struct clock_event_device *dev)
{
dev->event_handler = tick_handle_periodic;
if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
} else {
unsigned long seq;
ktime_t next;
do {
seq = read_seqbegin(&xtime_lock);
next = tick_next_period;
} while (read_seqretry(&xtime_lock, seq));
clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
for (;;) {
if (!clockevents_program_event(dev, next, ktime_get()))
return;
next = ktime_add(next, tick_period);
}
}
}
/*
* Setup the tick device
*/
static void tick_setup_device(struct tick_device *td,
struct clock_event_device *newdev, int cpu,
cpumask_t 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 == -1) {
tick_do_timer_cpu = cpu;
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 = newdev;
/*
* When the device is not per cpu, pin the interrupt to the
* current cpu:
*/
if (!cpus_equal(newdev->cpumask, cpumask))
irq_set_affinity(newdev->irq, cpumask);
if (td->mode == TICKDEV_MODE_PERIODIC)
tick_setup_periodic(newdev, 0);
}
/*
* Check, if the new registered device should be used.
*/
static int tick_check_new_device(struct clock_event_device *newdev)
{
struct clock_event_device *curdev;
struct tick_device *td;
int cpu, ret = NOTIFY_OK;
unsigned long flags;
cpumask_t cpumask;
spin_lock_irqsave(&tick_device_lock, flags);
cpu = smp_processor_id();
if (!cpu_isset(cpu, newdev->cpumask))
goto out;
td = &per_cpu(tick_cpu_device, cpu);
curdev = td->evtdev;
cpumask = cpumask_of_cpu(cpu);
/* cpu local device ? */
if (!cpus_equal(newdev->cpumask, cpumask)) {
/*
* If the cpu affinity of the device interrupt can not
* be set, ignore it.
*/
if (!irq_can_set_affinity(newdev->irq))
goto out_bc;
/*
* If we have a cpu local device already, do not replace it
* by a non cpu local device
*/
if (curdev && cpus_equal(curdev->cpumask, cpumask))
goto out_bc;
}
/*
* If we have an active device, then check the rating and the oneshot
* feature.
*/
if (curdev) {
/*
* Check the rating
*/
if (curdev->rating >= newdev->rating)
goto out;
}
/*
* Replace the eventually existing device by the new
* device.
*/
clockevents_exchange_device(curdev, newdev);
tick_setup_device(td, newdev, cpu, cpumask);
ret = NOTIFY_STOP;
out:
spin_unlock_irqrestore(&tick_device_lock, flags);
return ret;
}
/*
* Shutdown an event device on a given cpu:
*
* This is called on a life CPU, when a CPU is dead. So we cannot
* access the hardware device itself.
* We just set the mode and remove it from the lists.
*/
static void tick_shutdown(unsigned int *cpup)
{
struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
struct clock_event_device *dev = td->evtdev;
unsigned long flags;
spin_lock_irqsave(&tick_device_lock, flags);
td->mode = TICKDEV_MODE_PERIODIC;
if (dev) {
/*
* Prevent that the clock events layer tries to call
* the set mode function!
*/
dev->mode = CLOCK_EVT_MODE_UNUSED;
clockevents_exchange_device(dev, NULL);
td->evtdev = NULL;
}
spin_unlock_irqrestore(&tick_device_lock, flags);
}
/*
* Notification about clock event devices
*/
static int tick_notify(struct notifier_block *nb, unsigned long reason,
void *dev)
{
switch (reason) {
case CLOCK_EVT_NOTIFY_ADD:
return tick_check_new_device(dev);
case CLOCK_EVT_NOTIFY_CPU_DEAD:
tick_shutdown(dev);
break;
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block tick_notifier = {
.notifier_call = tick_notify,
};
/**
* tick_init - initialize the tick control
*
* Register the notifier with the clockevents framework
*/
void __init tick_init(void)
{
clockevents_register_notifier(&tick_notifier);
}
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