Re: [patch 02/12] hrtimer: Provide hrtimer_start_range_ns_user()

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Apr 07, 2026 at 10:54:22AM +0200, Thomas Gleixner wrote:

> +static inline bool hrtimer_check_user_timer(struct hrtimer *timer)
> +{
> +	struct hrtimer_cpu_base *cpu_base = timer->base->cpu_base;
> +	ktime_t expires;
> +
> +	/*
> +	 * This uses soft expires because that's the user provided
> +	 * expiry time, while expires can be further in the past
> +	 * due to a slack value added to the user expiry time.
> +	 */
> +	expires = hrtimer_get_softexpires(timer);
> +
> +	/* Convert to monotonic */
> +	expires = ktime_sub(expires, timer->base->offset);
> +
> +	/*
> +	 * Check whether this timer will end up as the first expiring timer in
> +	 * the CPU base. If not, no further checks required as it's then
> +	 * guaranteed to expire in the future.
> +	 */
> +	if (expires >= cpu_base->expires_next)
> +		return true;
> +
> +	/* Validate that the expiry time is in the future. */
> +	if (expires > ktime_get())
> +		return true;
> +
> +	debug_deactivate(timer);
> +	__remove_hrtimer(timer, timer->base, HRTIMER_STATE_INACTIVE, false);
> +	trace_hrtimer_start_expired(timer);
> +	return false;
> +}
> +
> +static bool hrtimer_reprogram_user(struct hrtimer *timer)
> +{
> +	if (!hrtimer_check_user_timer(timer))
> +		return false;
> +	hrtimer_reprogram(timer, true);
> +	return true;
> +}
> +
> +static bool hrtimer_force_reprogram_user(struct hrtimer *timer)
> +{
> +	bool ret = hrtimer_check_user_timer(timer);
> +
> +	/*
> +	 * The base must always be reevaluated, independent of the result
> +	 * above because the timer was the first pending timer.
> +	 */
> +	hrtimer_force_reprogram(timer->base->cpu_base, 1);
> +	return ret;
> +}
> +
> +/**
> + * hrtimer_start_range_ns_user - (re)start an user controlled hrtimer
> + * @timer:	the timer to be added
> + * @tim:	expiry time
> + * @delta_ns:	"slack" range for the timer
> + * @mode:	timer mode: absolute (HRTIMER_MODE_ABS) or
> + *		relative (HRTIMER_MODE_REL), and pinned (HRTIMER_MODE_PINNED);
> + *		softirq based mode is considered for debug purpose only!
> + *
> + * Returns: True when the timer was queued, false if it was already expired
> + *
> + * This function cannot invoke the timer callback for expired timers as it might
> + * be called under a lock which the timer callback needs to acquire. So the
> + * caller has to handle that case.
> + */
> +bool hrtimer_start_range_ns_user(struct hrtimer *timer, ktime_t tim,
> +				 u64 delta_ns, const enum hrtimer_mode mode)
> +{
> +	struct hrtimer_clock_base *base;
> +	unsigned long flags;
> +	bool ret = true;
> +
> +	base = lock_hrtimer_base(timer, &flags);
> +	switch (hrtimer_start_range_ns_common(timer, tim, delta_ns, mode, base)) {
> +	case HRTIMER_REPROGRAM:
> +		ret = hrtimer_reprogram_user(timer);
> +		break;
> +	case HRTIMER_REPROGRAM_FORCE:
> +		ret = hrtimer_force_reprogram_user(timer);
> +		break;
> +	}
> +	unlock_hrtimer_base(timer, &flags);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(hrtimer_start_range_ns_user);

Can we do that hrtimer_check_user_timer() in
hrtimer_start_range_ns_user() and then not duplicate
hrtimer_*reprogram() ?