Commit 4b41308d authored by John Stultz's avatar John Stultz
Browse files

alarmtimers: Change alarmtimer functions to return alarmtimer_restart values 



In order to properly fix the denial of service issue with high freq
periodic alarm timers, we need to push the re-arming logic into the
alarm timer handler, much as the hrtimer code does.

This patch introduces alarmtimer_restart enum and changes the
alarmtimer handler declarations to use it as a return value. Further,
to ease following changes, it extends the alarmtimer handler functions
to also take the time at expiration. No logic is yet modified.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 6af7e471

include/linux/alarmtimer.h

+7 −2
Original line number Diff line number Diff line
@@ -13,6 +13,11 @@ enum alarmtimer_type { 
	ALARM_NUMTYPE,

};



enum alarmtimer_restart {

	ALARMTIMER_NORESTART,

	ALARMTIMER_RESTART,

};



/**

 * struct alarm - Alarm timer structure

 * @node:	timerqueue node for adding to the event list this value
@@ -26,14 +31,14 @@ enum alarmtimer_type { 
struct alarm {

	struct timerqueue_node	node;

	ktime_t			period;

	void			(*function)(struct alarm *);

	enum alarmtimer_restart	(*function)(struct alarm *, ktime_t now);

	enum alarmtimer_type	type;

	bool			enabled;

	void			*data;

};



void alarm_init(struct alarm *alarm, enum alarmtimer_type type,

		void (*function)(struct alarm *));

		enum alarmtimer_restart (*function)(struct alarm *, ktime_t));

void alarm_start(struct alarm *alarm, ktime_t start, ktime_t period);

void alarm_cancel(struct alarm *alarm);

kernel/time/alarmtimer.c

+9 −4
Original line number Diff line number Diff line
@@ -196,7 +196,7 @@ static enum hrtimer_restart alarmtimer_fired(struct hrtimer *timer) 
		}

		spin_unlock_irqrestore(&base->lock, flags);

		if (alarm->function)

			alarm->function(alarm);

			alarm->function(alarm, now);

		spin_lock_irqsave(&base->lock, flags);

	}
@@ -299,7 +299,7 @@ static void alarmtimer_freezerset(ktime_t absexp, enum alarmtimer_type type) 
 * @function: callback that is run when the alarm fires

 */

void alarm_init(struct alarm *alarm, enum alarmtimer_type type,

		void (*function)(struct alarm *))

		enum alarmtimer_restart (*function)(struct alarm *, ktime_t))

{

	timerqueue_init(&alarm->node);

	alarm->period = ktime_set(0, 0);
@@ -365,12 +365,15 @@ static enum alarmtimer_type clock2alarm(clockid_t clockid) 
 *

 * Posix timer callback for expired alarm timers.

 */

static void alarm_handle_timer(struct alarm *alarm)

static enum alarmtimer_restart alarm_handle_timer(struct alarm *alarm,

							ktime_t now)

{

	struct k_itimer *ptr = container_of(alarm, struct k_itimer,

						it.alarmtimer);

	if (posix_timer_event(ptr, 0) != 0)

		ptr->it_overrun++;



	return ALARMTIMER_NORESTART;

}



/**
@@ -509,13 +512,15 @@ static int alarm_timer_set(struct k_itimer *timr, int flags, 
 *

 * Wakes up the task that set the alarmtimer

 */

static void alarmtimer_nsleep_wakeup(struct alarm *alarm)

static enum alarmtimer_restart alarmtimer_nsleep_wakeup(struct alarm *alarm,

								ktime_t now)

{

	struct task_struct *task = (struct task_struct *)alarm->data;



	alarm->data = NULL;

	if (task)

		wake_up_process(task);

	return ALARMTIMER_NORESTART;

}



/**

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