Commit 8f02e356 authored by Nam Cao's avatar Nam Cao Committed by Thomas Gleixner
Browse files

hrtimers: Introduce hrtimer_update_function() 



Some users of hrtimer need to change the callback function after the
initial setup. They write to hrtimer::function directly.

That's not safe under all circumstances as the write is lockless and a
concurrent timer expiry might end up using the wrong function pointer.

Introduce hrtimer_update_function(), which also performs runtime checks
whether it is safe to modify the callback.

This allows to make hrtimer::function private once all users are converted.

Signed-off-by: default avatarNam Cao <namcao@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20a937b0ae09ad54b5b6d86eabead7c570f1b72e.1730386209.git.namcao@linutronix.de
parent c9bd83ab

include/linux/hrtimer.h

+22 −0
Original line number Diff line number Diff line
@@ -327,6 +327,28 @@ static inline int hrtimer_callback_running(struct hrtimer *timer) 
	return timer->base->running == timer;

}



/**

 * hrtimer_update_function - Update the timer's callback function

 * @timer:	Timer to update

 * @function:	New callback function

 *

 * Only safe to call if the timer is not enqueued. Can be called in the callback function if the

 * timer is not enqueued at the same time (see the comments above HRTIMER_STATE_ENQUEUED).

 */

static inline void hrtimer_update_function(struct hrtimer *timer,

					   enum hrtimer_restart (*function)(struct hrtimer *))

{

	guard(raw_spinlock_irqsave)(&timer->base->cpu_base->lock);



	if (WARN_ON_ONCE(hrtimer_is_queued(timer)))

		return;



	if (WARN_ON_ONCE(!function))

		return;



	timer->function = function;

}



/* Forward a hrtimer so it expires after now: */

extern u64

hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);