linux/kernel/time/alarmtimer.c
John Stultz 1c6b39ad3f alarmtimers: Return -ENOTSUPP if no RTC device is present
Toralf Förster and Richard Weinberger noted that if there is
no RTC device, the alarm timers core prints out an annoying
"ALARM timers will not wake from suspend" message.

This warning has been removed in a previous patch, however
the issue still remains:  The original idea was to support
alarm timers even if there was no rtc device, as long as the
system didn't go into suspend.

However, after further consideration, communicating to the application
that alarmtimers are not fully functional seems like the better
solution.

So this patch makes it so we return -ENOTSUPP to any posix _ALARM
clockid calls if there is no backing RTC device on the system.

Further this changes the behavior where when there is no rtc device
we will check for one on clock_getres, clock_gettime, timer_create,
and timer_nsleep instead of on suspend.

CC: Toralf Förster <toralf.foerster@gmx.de>
CC: Richard Weinberger <richard@nod.at
CC: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Reported by: Richard Weinberger <richard@nod.at>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2011-06-21 16:32:28 -07:00

721 lines
18 KiB
C

/*
* Alarmtimer interface
*
* This interface provides a timer which is similarto hrtimers,
* but triggers a RTC alarm if the box is suspend.
*
* This interface is influenced by the Android RTC Alarm timer
* interface.
*
* Copyright (C) 2010 IBM Corperation
*
* Author: John Stultz <john.stultz@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/time.h>
#include <linux/hrtimer.h>
#include <linux/timerqueue.h>
#include <linux/rtc.h>
#include <linux/alarmtimer.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/posix-timers.h>
#include <linux/workqueue.h>
#include <linux/freezer.h>
/**
* struct alarm_base - Alarm timer bases
* @lock: Lock for syncrhonized access to the base
* @timerqueue: Timerqueue head managing the list of events
* @timer: hrtimer used to schedule events while running
* @gettime: Function to read the time correlating to the base
* @base_clockid: clockid for the base
*/
static struct alarm_base {
spinlock_t lock;
struct timerqueue_head timerqueue;
struct hrtimer timer;
ktime_t (*gettime)(void);
clockid_t base_clockid;
} alarm_bases[ALARM_NUMTYPE];
/* freezer delta & lock used to handle clock_nanosleep triggered wakeups */
static ktime_t freezer_delta;
static DEFINE_SPINLOCK(freezer_delta_lock);
#ifdef CONFIG_RTC_CLASS
/* rtc timer and device for setting alarm wakeups at suspend */
static struct rtc_timer rtctimer;
static struct rtc_device *rtcdev;
static DEFINE_SPINLOCK(rtcdev_lock);
/**
* has_wakealarm - check rtc device has wakealarm ability
* @dev: current device
* @name_ptr: name to be returned
*
* This helper function checks to see if the rtc device can wake
* from suspend.
*/
static int has_wakealarm(struct device *dev, void *name_ptr)
{
struct rtc_device *candidate = to_rtc_device(dev);
if (!candidate->ops->set_alarm)
return 0;
if (!device_may_wakeup(candidate->dev.parent))
return 0;
*(const char **)name_ptr = dev_name(dev);
return 1;
}
/**
* alarmtimer_get_rtcdev - Return selected rtcdevice
*
* This function returns the rtc device to use for wakealarms.
* If one has not already been chosen, it checks to see if a
* functional rtc device is available.
*/
static struct rtc_device *alarmtimer_get_rtcdev(void)
{
struct device *dev;
char *str;
unsigned long flags;
struct rtc_device *ret;
spin_lock_irqsave(&rtcdev_lock, flags);
if (!rtcdev) {
/* Find an rtc device and init the rtc_timer */
dev = class_find_device(rtc_class, NULL, &str, has_wakealarm);
/* If we have a device then str is valid. See has_wakealarm() */
if (dev) {
rtcdev = rtc_class_open(str);
/*
* Drop the reference we got in class_find_device,
* rtc_open takes its own.
*/
put_device(dev);
rtc_timer_init(&rtctimer, NULL, NULL);
}
}
ret = rtcdev;
spin_unlock_irqrestore(&rtcdev_lock, flags);
return ret;
}
#else
#define alarmtimer_get_rtcdev() (0)
#define rtcdev (0)
#endif
/**
* alarmtimer_enqueue - Adds an alarm timer to an alarm_base timerqueue
* @base: pointer to the base where the timer is being run
* @alarm: pointer to alarm being enqueued.
*
* Adds alarm to a alarm_base timerqueue and if necessary sets
* an hrtimer to run.
*
* Must hold base->lock when calling.
*/
static void alarmtimer_enqueue(struct alarm_base *base, struct alarm *alarm)
{
timerqueue_add(&base->timerqueue, &alarm->node);
if (&alarm->node == timerqueue_getnext(&base->timerqueue)) {
hrtimer_try_to_cancel(&base->timer);
hrtimer_start(&base->timer, alarm->node.expires,
HRTIMER_MODE_ABS);
}
}
/**
* alarmtimer_remove - Removes an alarm timer from an alarm_base timerqueue
* @base: pointer to the base where the timer is running
* @alarm: pointer to alarm being removed
*
* Removes alarm to a alarm_base timerqueue and if necessary sets
* a new timer to run.
*
* Must hold base->lock when calling.
*/
static void alarmtimer_remove(struct alarm_base *base, struct alarm *alarm)
{
struct timerqueue_node *next = timerqueue_getnext(&base->timerqueue);
timerqueue_del(&base->timerqueue, &alarm->node);
if (next == &alarm->node) {
hrtimer_try_to_cancel(&base->timer);
next = timerqueue_getnext(&base->timerqueue);
if (!next)
return;
hrtimer_start(&base->timer, next->expires, HRTIMER_MODE_ABS);
}
}
/**
* alarmtimer_fired - Handles alarm hrtimer being fired.
* @timer: pointer to hrtimer being run
*
* When a alarm timer fires, this runs through the timerqueue to
* see which alarms expired, and runs those. If there are more alarm
* timers queued for the future, we set the hrtimer to fire when
* when the next future alarm timer expires.
*/
static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer)
{
struct alarm_base *base = container_of(timer, struct alarm_base, timer);
struct timerqueue_node *next;
unsigned long flags;
ktime_t now;
int ret = HRTIMER_NORESTART;
spin_lock_irqsave(&base->lock, flags);
now = base->gettime();
while ((next = timerqueue_getnext(&base->timerqueue))) {
struct alarm *alarm;
ktime_t expired = next->expires;
if (expired.tv64 >= now.tv64)
break;
alarm = container_of(next, struct alarm, node);
timerqueue_del(&base->timerqueue, &alarm->node);
alarm->enabled = 0;
/* Re-add periodic timers */
if (alarm->period.tv64) {
alarm->node.expires = ktime_add(expired, alarm->period);
timerqueue_add(&base->timerqueue, &alarm->node);
alarm->enabled = 1;
}
spin_unlock_irqrestore(&base->lock, flags);
if (alarm->function)
alarm->function(alarm);
spin_lock_irqsave(&base->lock, flags);
}
if (next) {
hrtimer_set_expires(&base->timer, next->expires);
ret = HRTIMER_RESTART;
}
spin_unlock_irqrestore(&base->lock, flags);
return ret;
}
#ifdef CONFIG_RTC_CLASS
/**
* alarmtimer_suspend - Suspend time callback
* @dev: unused
* @state: unused
*
* When we are going into suspend, we look through the bases
* to see which is the soonest timer to expire. We then
* set an rtc timer to fire that far into the future, which
* will wake us from suspend.
*/
static int alarmtimer_suspend(struct device *dev)
{
struct rtc_time tm;
ktime_t min, now;
unsigned long flags;
struct rtc_device *rtc;
int i;
spin_lock_irqsave(&freezer_delta_lock, flags);
min = freezer_delta;
freezer_delta = ktime_set(0, 0);
spin_unlock_irqrestore(&freezer_delta_lock, flags);
rtc = rtcdev;
/* If we have no rtcdev, just return */
if (!rtc)
return 0;
/* Find the soonest timer to expire*/
for (i = 0; i < ALARM_NUMTYPE; i++) {
struct alarm_base *base = &alarm_bases[i];
struct timerqueue_node *next;
ktime_t delta;
spin_lock_irqsave(&base->lock, flags);
next = timerqueue_getnext(&base->timerqueue);
spin_unlock_irqrestore(&base->lock, flags);
if (!next)
continue;
delta = ktime_sub(next->expires, base->gettime());
if (!min.tv64 || (delta.tv64 < min.tv64))
min = delta;
}
if (min.tv64 == 0)
return 0;
/* XXX - Should we enforce a minimum sleep time? */
WARN_ON(min.tv64 < NSEC_PER_SEC);
/* Setup an rtc timer to fire that far in the future */
rtc_timer_cancel(rtc, &rtctimer);
rtc_read_time(rtc, &tm);
now = rtc_tm_to_ktime(tm);
now = ktime_add(now, min);
rtc_timer_start(rtc, &rtctimer, now, ktime_set(0, 0));
return 0;
}
#else
static int alarmtimer_suspend(struct device *dev)
{
return 0;
}
#endif
static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type)
{
ktime_t delta;
unsigned long flags;
struct alarm_base *base = &alarm_bases[type];
delta = ktime_sub(absexp, base->gettime());
spin_lock_irqsave(&freezer_delta_lock, flags);
if (!freezer_delta.tv64 || (delta.tv64 < freezer_delta.tv64))
freezer_delta = delta;
spin_unlock_irqrestore(&freezer_delta_lock, flags);
}
/**
* alarm_init - Initialize an alarm structure
* @alarm: ptr to alarm to be initialized
* @type: the type of the alarm
* @function: callback that is run when the alarm fires
*/
void alarm_init(struct alarm *alarm, enum alarmtimer_type type,
void (*function)(struct alarm *))
{
timerqueue_init(&alarm->node);
alarm->period = ktime_set(0, 0);
alarm->function = function;
alarm->type = type;
alarm->enabled = 0;
}
/**
* alarm_start - Sets an alarm to fire
* @alarm: ptr to alarm to set
* @start: time to run the alarm
* @period: period at which the alarm will recur
*/
void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period)
{
struct alarm_base *base = &alarm_bases[alarm->type];
unsigned long flags;
spin_lock_irqsave(&base->lock, flags);
if (alarm->enabled)
alarmtimer_remove(base, alarm);
alarm->node.expires = start;
alarm->period = period;
alarmtimer_enqueue(base, alarm);
alarm->enabled = 1;
spin_unlock_irqrestore(&base->lock, flags);
}
/**
* alarm_cancel - Tries to cancel an alarm timer
* @alarm: ptr to alarm to be canceled
*/
void alarm_cancel(struct alarm *alarm)
{
struct alarm_base *base = &alarm_bases[alarm->type];
unsigned long flags;
spin_lock_irqsave(&base->lock, flags);
if (alarm->enabled)
alarmtimer_remove(base, alarm);
alarm->enabled = 0;
spin_unlock_irqrestore(&base->lock, flags);
}
/**
* clock2alarm - helper that converts from clockid to alarmtypes
* @clockid: clockid.
*/
static enum alarmtimer_type clock2alarm(clockid_t clockid)
{
if (clockid == CLOCK_REALTIME_ALARM)
return ALARM_REALTIME;
if (clockid == CLOCK_BOOTTIME_ALARM)
return ALARM_BOOTTIME;
return -1;
}
/**
* alarm_handle_timer - Callback for posix timers
* @alarm: alarm that fired
*
* Posix timer callback for expired alarm timers.
*/
static void alarm_handle_timer(struct alarm *alarm)
{
struct k_itimer *ptr = container_of(alarm, struct k_itimer,
it.alarmtimer);
if (posix_timer_event(ptr, 0) != 0)
ptr->it_overrun++;
}
/**
* alarm_clock_getres - posix getres interface
* @which_clock: clockid
* @tp: timespec to fill
*
* Returns the granularity of underlying alarm base clock
*/
static int alarm_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
clockid_t baseid = alarm_bases[clock2alarm(which_clock)].base_clockid;
if (!alarmtimer_get_rtcdev())
return -ENOTSUPP;
return hrtimer_get_res(baseid, tp);
}
/**
* alarm_clock_get - posix clock_get interface
* @which_clock: clockid
* @tp: timespec to fill.
*
* Provides the underlying alarm base time.
*/
static int alarm_clock_get(clockid_t which_clock, struct timespec *tp)
{
struct alarm_base *base = &alarm_bases[clock2alarm(which_clock)];
if (!alarmtimer_get_rtcdev())
return -ENOTSUPP;
*tp = ktime_to_timespec(base->gettime());
return 0;
}
/**
* alarm_timer_create - posix timer_create interface
* @new_timer: k_itimer pointer to manage
*
* Initializes the k_itimer structure.
*/
static int alarm_timer_create(struct k_itimer *new_timer)
{
enum alarmtimer_type type;
struct alarm_base *base;
if (!alarmtimer_get_rtcdev())
return -ENOTSUPP;
if (!capable(CAP_WAKE_ALARM))
return -EPERM;
type = clock2alarm(new_timer->it_clock);
base = &alarm_bases[type];
alarm_init(&new_timer->it.alarmtimer, type, alarm_handle_timer);
return 0;
}
/**
* alarm_timer_get - posix timer_get interface
* @new_timer: k_itimer pointer
* @cur_setting: itimerspec data to fill
*
* Copies the itimerspec data out from the k_itimer
*/
static void alarm_timer_get(struct k_itimer *timr,
struct itimerspec *cur_setting)
{
cur_setting->it_interval =
ktime_to_timespec(timr->it.alarmtimer.period);
cur_setting->it_value =
ktime_to_timespec(timr->it.alarmtimer.node.expires);
return;
}
/**
* alarm_timer_del - posix timer_del interface
* @timr: k_itimer pointer to be deleted
*
* Cancels any programmed alarms for the given timer.
*/
static int alarm_timer_del(struct k_itimer *timr)
{
if (!rtcdev)
return -ENOTSUPP;
alarm_cancel(&timr->it.alarmtimer);
return 0;
}
/**
* alarm_timer_set - posix timer_set interface
* @timr: k_itimer pointer to be deleted
* @flags: timer flags
* @new_setting: itimerspec to be used
* @old_setting: itimerspec being replaced
*
* Sets the timer to new_setting, and starts the timer.
*/
static int alarm_timer_set(struct k_itimer *timr, int flags,
struct itimerspec *new_setting,
struct itimerspec *old_setting)
{
if (!rtcdev)
return -ENOTSUPP;
/* Save old values */
old_setting->it_interval =
ktime_to_timespec(timr->it.alarmtimer.period);
old_setting->it_value =
ktime_to_timespec(timr->it.alarmtimer.node.expires);
/* If the timer was already set, cancel it */
alarm_cancel(&timr->it.alarmtimer);
/* start the timer */
alarm_start(&timr->it.alarmtimer,
timespec_to_ktime(new_setting->it_value),
timespec_to_ktime(new_setting->it_interval));
return 0;
}
/**
* alarmtimer_nsleep_wakeup - Wakeup function for alarm_timer_nsleep
* @alarm: ptr to alarm that fired
*
* Wakes up the task that set the alarmtimer
*/
static void alarmtimer_nsleep_wakeup(struct alarm *alarm)
{
struct task_struct *task = (struct task_struct *)alarm->data;
alarm->data = NULL;
if (task)
wake_up_process(task);
}
/**
* alarmtimer_do_nsleep - Internal alarmtimer nsleep implementation
* @alarm: ptr to alarmtimer
* @absexp: absolute expiration time
*
* Sets the alarm timer and sleeps until it is fired or interrupted.
*/
static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp)
{
alarm->data = (void *)current;
do {
set_current_state(TASK_INTERRUPTIBLE);
alarm_start(alarm, absexp, ktime_set(0, 0));
if (likely(alarm->data))
schedule();
alarm_cancel(alarm);
} while (alarm->data && !signal_pending(current));
__set_current_state(TASK_RUNNING);
return (alarm->data == NULL);
}
/**
* update_rmtp - Update remaining timespec value
* @exp: expiration time
* @type: timer type
* @rmtp: user pointer to remaining timepsec value
*
* Helper function that fills in rmtp value with time between
* now and the exp value
*/
static int update_rmtp(ktime_t exp, enum alarmtimer_type type,
struct timespec __user *rmtp)
{
struct timespec rmt;
ktime_t rem;
rem = ktime_sub(exp, alarm_bases[type].gettime());
if (rem.tv64 <= 0)
return 0;
rmt = ktime_to_timespec(rem);
if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
return -EFAULT;
return 1;
}
/**
* alarm_timer_nsleep_restart - restartblock alarmtimer nsleep
* @restart: ptr to restart block
*
* Handles restarted clock_nanosleep calls
*/
static long __sched alarm_timer_nsleep_restart(struct restart_block *restart)
{
enum alarmtimer_type type = restart->nanosleep.clockid;
ktime_t exp;
struct timespec __user *rmtp;
struct alarm alarm;
int ret = 0;
exp.tv64 = restart->nanosleep.expires;
alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);
if (alarmtimer_do_nsleep(&alarm, exp))
goto out;
if (freezing(current))
alarmtimer_freezerset(exp, type);
rmtp = restart->nanosleep.rmtp;
if (rmtp) {
ret = update_rmtp(exp, type, rmtp);
if (ret <= 0)
goto out;
}
/* The other values in restart are already filled in */
ret = -ERESTART_RESTARTBLOCK;
out:
return ret;
}
/**
* alarm_timer_nsleep - alarmtimer nanosleep
* @which_clock: clockid
* @flags: determins abstime or relative
* @tsreq: requested sleep time (abs or rel)
* @rmtp: remaining sleep time saved
*
* Handles clock_nanosleep calls against _ALARM clockids
*/
static int alarm_timer_nsleep(const clockid_t which_clock, int flags,
struct timespec *tsreq, struct timespec __user *rmtp)
{
enum alarmtimer_type type = clock2alarm(which_clock);
struct alarm alarm;
ktime_t exp;
int ret = 0;
struct restart_block *restart;
if (!alarmtimer_get_rtcdev())
return -ENOTSUPP;
if (!capable(CAP_WAKE_ALARM))
return -EPERM;
alarm_init(&alarm, type, alarmtimer_nsleep_wakeup);
exp = timespec_to_ktime(*tsreq);
/* Convert (if necessary) to absolute time */
if (flags != TIMER_ABSTIME) {
ktime_t now = alarm_bases[type].gettime();
exp = ktime_add(now, exp);
}
if (alarmtimer_do_nsleep(&alarm, exp))
goto out;
if (freezing(current))
alarmtimer_freezerset(exp, type);
/* abs timers don't set remaining time or restart */
if (flags == TIMER_ABSTIME) {
ret = -ERESTARTNOHAND;
goto out;
}
if (rmtp) {
ret = update_rmtp(exp, type, rmtp);
if (ret <= 0)
goto out;
}
restart = &current_thread_info()->restart_block;
restart->fn = alarm_timer_nsleep_restart;
restart->nanosleep.clockid = type;
restart->nanosleep.expires = exp.tv64;
restart->nanosleep.rmtp = rmtp;
ret = -ERESTART_RESTARTBLOCK;
out:
return ret;
}
/* Suspend hook structures */
static const struct dev_pm_ops alarmtimer_pm_ops = {
.suspend = alarmtimer_suspend,
};
static struct platform_driver alarmtimer_driver = {
.driver = {
.name = "alarmtimer",
.pm = &alarmtimer_pm_ops,
}
};
/**
* alarmtimer_init - Initialize alarm timer code
*
* This function initializes the alarm bases and registers
* the posix clock ids.
*/
static int __init alarmtimer_init(void)
{
int error = 0;
int i;
struct k_clock alarm_clock = {
.clock_getres = alarm_clock_getres,
.clock_get = alarm_clock_get,
.timer_create = alarm_timer_create,
.timer_set = alarm_timer_set,
.timer_del = alarm_timer_del,
.timer_get = alarm_timer_get,
.nsleep = alarm_timer_nsleep,
};
posix_timers_register_clock(CLOCK_REALTIME_ALARM, &alarm_clock);
posix_timers_register_clock(CLOCK_BOOTTIME_ALARM, &alarm_clock);
/* Initialize alarm bases */
alarm_bases[ALARM_REALTIME].base_clockid = CLOCK_REALTIME;
alarm_bases[ALARM_REALTIME].gettime = &ktime_get_real;
alarm_bases[ALARM_BOOTTIME].base_clockid = CLOCK_BOOTTIME;
alarm_bases[ALARM_BOOTTIME].gettime = &ktime_get_boottime;
for (i = 0; i < ALARM_NUMTYPE; i++) {
timerqueue_init_head(&alarm_bases[i].timerqueue);
spin_lock_init(&alarm_bases[i].lock);
hrtimer_init(&alarm_bases[i].timer,
alarm_bases[i].base_clockid,
HRTIMER_MODE_ABS);
alarm_bases[i].timer.function = alarmtimer_fired;
}
error = platform_driver_register(&alarmtimer_driver);
platform_device_register_simple("alarmtimer", -1, NULL, 0);
return error;
}
device_initcall(alarmtimer_init);