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hrtimers: Introduce hrtimer_update_function()

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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: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20a937b0ae09ad54b5b6d86eabead7c570f1b72e.1730386209.git.namcao@linutronix.de
This commit is contained in:
Nam Cao 2024-10-31 16:14:23 +01:00 committed by Thomas Gleixner
parent c9bd83abfe
commit 8f02e3563b
1 changed files with 22 additions and 0 deletions
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22
include/linux/hrtimer.h
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@ -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);