Commit 03e13cf5 authored by Thomas Gleixner's avatar Thomas Gleixner

clockevents: Implement unbind functionality

Provide a sysfs interface to allow unbinding of clockevent
devices. The device is unbound if it is unused or if there is a
replacement device available. Unbinding of broadcast devices is not
supported as we don't want to foster that nonsense. If no replacement
device is available the unbind returns -EBUSY. Unbind is available
from the kernel and through sysfs, which is necessary to drop the
module refcount.
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130425143436.499216659@linutronix.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 45cb8e01
......@@ -141,6 +141,7 @@ static inline unsigned long div_sc(unsigned long ticks, unsigned long nsec,
extern u64 clockevent_delta2ns(unsigned long latch,
struct clock_event_device *evt);
extern void clockevents_register_device(struct clock_event_device *dev);
extern int clockevents_unbind_device(struct clock_event_device *ced, int cpu);
extern void clockevents_config(struct clock_event_device *dev, u32 freq);
extern void clockevents_config_and_register(struct clock_event_device *dev,
......
......@@ -25,6 +25,13 @@ static LIST_HEAD(clockevent_devices);
static LIST_HEAD(clockevents_released);
/* Protection for the above */
static DEFINE_RAW_SPINLOCK(clockevents_lock);
/* Protection for unbind operations */
static DEFINE_MUTEX(clockevents_mutex);
struct ce_unbind {
struct clock_event_device *ce;
int res;
};
/**
* clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
......@@ -245,6 +252,90 @@ static void clockevents_notify_released(void)
}
}
/*
* Try to install a replacement clock event device
*/
static int clockevents_replace(struct clock_event_device *ced)
{
struct clock_event_device *dev, *newdev = NULL;
list_for_each_entry(dev, &clockevent_devices, list) {
if (dev == ced || dev->mode != CLOCK_EVT_MODE_UNUSED)
continue;
if (!tick_check_replacement(newdev, dev))
continue;
if (!try_module_get(dev->owner))
continue;
if (newdev)
module_put(newdev->owner);
newdev = dev;
}
if (newdev) {
tick_install_replacement(newdev);
list_del_init(&ced->list);
}
return newdev ? 0 : -EBUSY;
}
/*
* Called with clockevents_mutex and clockevents_lock held
*/
static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
{
/* Fast track. Device is unused */
if (ced->mode == CLOCK_EVT_MODE_UNUSED) {
list_del_init(&ced->list);
return 0;
}
return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
}
/*
* SMP function call to unbind a device
*/
static void __clockevents_unbind(void *arg)
{
struct ce_unbind *cu = arg;
int res;
raw_spin_lock(&clockevents_lock);
res = __clockevents_try_unbind(cu->ce, smp_processor_id());
if (res == -EAGAIN)
res = clockevents_replace(cu->ce);
cu->res = res;
raw_spin_unlock(&clockevents_lock);
}
/*
* Issues smp function call to unbind a per cpu device. Called with
* clockevents_mutex held.
*/
static int clockevents_unbind(struct clock_event_device *ced, int cpu)
{
struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
return cu.res;
}
/*
* Unbind a clockevents device.
*/
int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
{
int ret;
mutex_lock(&clockevents_mutex);
ret = clockevents_unbind(ced, cpu);
mutex_unlock(&clockevents_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(clockevents_unbind);
/**
* clockevents_register_device - register a clock event device
* @dev: device to register
......@@ -487,6 +578,38 @@ static ssize_t sysfs_show_current_tick_dev(struct device *dev,
}
static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
/* We don't support the abomination of removable broadcast devices */
static ssize_t sysfs_unbind_tick_dev(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
char name[CS_NAME_LEN];
size_t ret = sysfs_get_uname(buf, name, count);
struct clock_event_device *ce;
if (ret < 0)
return ret;
ret = -ENODEV;
mutex_lock(&clockevents_mutex);
raw_spin_lock_irq(&clockevents_lock);
list_for_each_entry(ce, &clockevent_devices, list) {
if (!strcmp(ce->name, name)) {
ret = __clockevents_try_unbind(ce, dev->id);
break;
}
}
raw_spin_unlock_irq(&clockevents_lock);
/*
* We hold clockevents_mutex, so ce can't go away
*/
if (ret == -EAGAIN)
ret = clockevents_unbind(ce, dev->id);
mutex_unlock(&clockevents_mutex);
return ret ? ret : count;
}
static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
static struct device tick_bc_dev = {
.init_name = "broadcast",
......@@ -529,6 +652,8 @@ static int __init tick_init_sysfs(void)
err = device_register(dev);
if (!err)
err = device_create_file(dev, &dev_attr_current_device);
if (!err)
err = device_create_file(dev, &dev_attr_unbind_device);
if (err)
return err;
}
......
......@@ -31,6 +31,8 @@
#include <linux/tick.h>
#include <linux/kthread.h>
#include "tick-internal.h"
void timecounter_init(struct timecounter *tc,
const struct cyclecounter *cc,
u64 start_tstamp)
......@@ -174,7 +176,6 @@ clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
static struct clocksource *curr_clocksource;
static LIST_HEAD(clocksource_list);
static DEFINE_MUTEX(clocksource_mutex);
#define CS_NAME_LEN 32
static char override_name[CS_NAME_LEN];
static int finished_booting;
......@@ -864,7 +865,7 @@ sysfs_show_current_clocksources(struct device *dev,
return count;
}
static size_t clocksource_get_uname(const char *buf, char *dst, size_t cnt)
size_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
{
size_t ret = cnt;
......@@ -899,7 +900,7 @@ static ssize_t sysfs_override_clocksource(struct device *dev,
mutex_lock(&clocksource_mutex);
ret = clocksource_get_uname(buf, override_name, count);
ret = sysfs_get_uname(buf, override_name, count);
if (ret >= 0)
clocksource_select();
......@@ -925,7 +926,7 @@ static ssize_t sysfs_unbind_clocksource(struct device *dev,
char name[CS_NAME_LEN];
size_t ret;
ret = clocksource_get_uname(buf, name, count);
ret = sysfs_get_uname(buf, name, count);
if (ret < 0)
return ret;
......
......@@ -205,6 +205,17 @@ static void tick_setup_device(struct tick_device *td,
tick_setup_oneshot(newdev, handler, next_event);
}
void tick_install_replacement(struct clock_event_device *newdev)
{
struct tick_device *td = &__get_cpu_var(tick_cpu_device);
int cpu = smp_processor_id();
clockevents_exchange_device(td->evtdev, newdev);
tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
tick_oneshot_notify();
}
static bool tick_check_percpu(struct clock_event_device *curdev,
struct clock_event_device *newdev, int cpu)
{
......@@ -236,6 +247,19 @@ static bool tick_check_preferred(struct clock_event_device *curdev,
return !curdev || newdev->rating > curdev->rating;
}
/*
* Check whether the new device is a better fit than curdev. curdev
* can be NULL !
*/
bool tick_check_replacement(struct clock_event_device *curdev,
struct clock_event_device *newdev)
{
if (tick_check_percpu(curdev, newdev, smp_processor_id()))
return false;
return tick_check_preferred(curdev, newdev);
}
/*
* Check, if the new registered device should be used. Called with
* clockevents_lock held and interrupts disabled.
......
......@@ -11,6 +11,8 @@ extern seqlock_t jiffies_lock;
#define TICK_DO_TIMER_NONE -1
#define TICK_DO_TIMER_BOOT -2
#define CS_NAME_LEN 32
DECLARE_PER_CPU(struct tick_device, tick_cpu_device);
extern ktime_t tick_next_period;
extern ktime_t tick_period;
......@@ -23,9 +25,14 @@ extern void tick_handover_do_timer(int *cpup);
extern void tick_shutdown(unsigned int *cpup);
extern void tick_suspend(void);
extern void tick_resume(void);
extern bool tick_check_replacement(struct clock_event_device *curdev,
struct clock_event_device *newdev);
extern void tick_install_replacement(struct clock_event_device *dev);
extern void clockevents_shutdown(struct clock_event_device *dev);
extern size_t sysfs_get_uname(const char *buf, char *dst, size_t cnt);
/*
* NO_HZ / high resolution timer shared code
*/
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment