Commit f8381cba authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Linus Torvalds
Browse files

[PATCH] tick-management: broadcast functionality



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: 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 906568c9
obj-y += ntp.o clocksource.o jiffies.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += clockevents.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS) += tick-common.o
obj-$(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) += tick-broadcast.o
/*
* 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/irq.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/tick.h>
#include "tick-internal.h"
/*
* Broadcast support for broken x86 hardware, where the local apic
* timer stops in C3 state.
*/
struct tick_device tick_broadcast_device;
static cpumask_t tick_broadcast_mask;
DEFINE_SPINLOCK(tick_broadcast_lock);
/*
* Start the device in periodic mode
*/
static void tick_broadcast_start_periodic(struct clock_event_device *bc)
{
if (bc && bc->mode == CLOCK_EVT_MODE_SHUTDOWN)
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)
{
if (tick_broadcast_device.evtdev ||
(dev->features & CLOCK_EVT_FEAT_C3STOP))
return 0;
clockevents_exchange_device(NULL, dev);
tick_broadcast_device.evtdev = dev;
if (!cpus_empty(tick_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;
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;
cpu_set(cpu, tick_broadcast_mask);
tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
ret = 1;
}
spin_unlock_irqrestore(&tick_broadcast_lock, flags);
return ret;
}
/*
* Broadcast the event to the cpus, which are set in the mask
*/
int tick_do_broadcast(cpumask_t mask)
{
int ret = 0, cpu = smp_processor_id();
struct tick_device *td;
/*
* Check, if the current cpu is in the mask
*/
if (cpu_isset(cpu, mask)) {
cpu_clear(cpu, mask);
td = &per_cpu(tick_cpu_device, cpu);
td->evtdev->event_handler(td->evtdev);
ret = 1;
}
if (!cpus_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)
*/
cpu = first_cpu(mask);
td = &per_cpu(tick_cpu_device, cpu);
td->evtdev->broadcast(mask);
ret = 1;
}
return ret;
}
/*
* Periodic broadcast:
* - invoke the broadcast handlers
*/
static void tick_do_periodic_broadcast(void)
{
cpumask_t mask;
spin_lock(&tick_broadcast_lock);
cpus_and(mask, cpu_online_map, tick_broadcast_mask);
tick_do_broadcast(mask);
spin_unlock(&tick_broadcast_lock);
}
/*
* Event handler for periodic broadcast ticks
*/
static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
{
dev->next_event.tv64 = KTIME_MAX;
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:
*/
for (;;) {
ktime_t next = ktime_add(dev->next_event, tick_period);
if (!clockevents_program_event(dev, next, ktime_get()))
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(void *why)
{
struct clock_event_device *bc, *dev;
struct tick_device *td;
unsigned long flags, *reason = why;
int cpu;
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 in broadcast mode forever or is it not
* affected by the powerstate ?
*/
if (!dev || !tick_device_is_functional(dev) ||
!(dev->features & CLOCK_EVT_FEAT_C3STOP))
goto out;
if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_ON) {
if (!cpu_isset(cpu, tick_broadcast_mask)) {
cpu_set(cpu, tick_broadcast_mask);
if (td->mode == TICKDEV_MODE_PERIODIC)
clockevents_set_mode(dev,
CLOCK_EVT_MODE_SHUTDOWN);
}
} else {
if (cpu_isset(cpu, tick_broadcast_mask)) {
cpu_clear(cpu, tick_broadcast_mask);
if (td->mode == TICKDEV_MODE_PERIODIC)
tick_setup_periodic(dev, 0);
}
}
if (cpus_empty(tick_broadcast_mask))
clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
else {
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
tick_broadcast_start_periodic(bc);
}
out:
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)
{
int cpu = get_cpu();
if (cpu == *oncpu)
tick_do_broadcast_on_off(&reason);
else
smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
&reason, 1, 1);
put_cpu();
}
/*
* 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;
spin_lock_irqsave(&tick_broadcast_lock, flags);
bc = tick_broadcast_device.evtdev;
cpu_clear(cpu, tick_broadcast_mask);
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
if (bc && cpus_empty(tick_broadcast_mask))
clockevents_set_mode(bc, CLOCK_EVT_MODE_SHUTDOWN);
}
spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
......@@ -20,17 +20,19 @@
#include <linux/sched.h>
#include <linux/tick.h>
#include "tick-internal.h"
/*
* Tick devices
*/
static DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
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;
ktime_t tick_next_period;
ktime_t tick_period;
static int tick_do_timer_cpu = -1;
static DEFINE_SPINLOCK(tick_device_lock);
DEFINE_SPINLOCK(tick_device_lock);
/*
* Periodic tick
......@@ -78,9 +80,13 @@ void tick_handle_periodic(struct clock_event_device *dev)
/*
* Setup the device for a periodic tick
*/
void tick_setup_periodic(struct clock_event_device *dev)
void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
{
dev->event_handler = tick_handle_periodic;
tick_set_periodic_handler(dev, broadcast);
/* Broadcast setup ? */
if (!tick_device_is_functional(dev))
return;
if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
......@@ -145,6 +151,15 @@ static void tick_setup_device(struct tick_device *td,
if (!cpus_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.
*/
if (tick_device_uses_broadcast(newdev, cpu))
return;
if (td->mode == TICKDEV_MODE_PERIODIC)
tick_setup_periodic(newdev, 0);
}
......@@ -197,19 +212,33 @@ static int tick_check_new_device(struct clock_event_device *newdev)
* Check the rating
*/
if (curdev->rating >= newdev->rating)
goto out;
goto out_bc;
}
/*
* Replace the eventually existing device by the new
* device.
* 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_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
curdev = NULL;
}
clockevents_exchange_device(curdev, newdev);
tick_setup_device(td, newdev, cpu, cpumask);
ret = NOTIFY_STOP;
spin_unlock_irqrestore(&tick_device_lock, flags);
return NOTIFY_STOP;
out_bc:
/*
* Can the new device be used as a broadcast device ?
*/
if (tick_check_broadcast_device(newdev))
ret = NOTIFY_STOP;
out:
spin_unlock_irqrestore(&tick_device_lock, flags);
return ret;
}
......@@ -251,7 +280,13 @@ static int tick_notify(struct notifier_block *nb, unsigned long reason,
case CLOCK_EVT_NOTIFY_ADD:
return tick_check_new_device(dev);
case CLOCK_EVT_NOTIFY_BROADCAST_ON:
case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
tick_broadcast_on_off(reason, dev);
break;
case CLOCK_EVT_NOTIFY_CPU_DEAD:
tick_shutdown_broadcast(dev);
tick_shutdown(dev);
break;
......
/*
* tick internal variable and functions used by low/high res code
*/
DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
extern spinlock_t tick_device_lock;
extern ktime_t tick_next_period;
extern ktime_t tick_period;
extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
extern void tick_handle_periodic(struct clock_event_device *dev);
/*
* Broadcasting support
*/
#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
extern int tick_do_broadcast(cpumask_t mask);
extern struct tick_device tick_broadcast_device;
extern spinlock_t tick_broadcast_lock;
extern int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu);
extern int tick_check_broadcast_device(struct clock_event_device *dev);
extern int tick_is_broadcast_device(struct clock_event_device *dev);
extern void tick_broadcast_on_off(unsigned long reason, int *oncpu);
extern void tick_shutdown_broadcast(unsigned int *cpup);
extern void
tick_set_periodic_handler(struct clock_event_device *dev, int broadcast);
#else /* !BROADCAST */
static inline int tick_check_broadcast_device(struct clock_event_device *dev)
{
return 0;
}
static inline int tick_is_broadcast_device(struct clock_event_device *dev)
{
return 0;
}
static inline int tick_device_uses_broadcast(struct clock_event_device *dev,
int cpu)
{
return 0;
}
static inline void tick_do_periodic_broadcast(struct clock_event_device *d) { }
static inline void tick_broadcast_on_off(unsigned long reason, int *oncpu) { }
static inline void tick_shutdown_broadcast(unsigned int *cpup) { }
/*
* Set the periodic handler in non broadcast mode
*/
static inline void tick_set_periodic_handler(struct clock_event_device *dev,
int broadcast)
{
dev->event_handler = tick_handle_periodic;
}
#endif /* !BROADCAST */
/*
* Check, if the device is functional or a dummy for broadcast
*/
static inline int tick_device_is_functional(struct clock_event_device *dev)
{
return !(dev->features & CLOCK_EVT_FEAT_DUMMY);
}
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