Commit 70b4cf84 authored by Anna-Maria Behnsen's avatar Anna-Maria Behnsen Committed by Thomas Gleixner
Browse files

timers: Split out "get next timer interrupt" functionality 



The functionality for getting the next timer interrupt in
get_next_timer_interrupt() is split into a separate function
fetch_next_timer_interrupt() to be usable by other call sites.

This is preparatory work for the conversion of the NOHZ timer
placement to a pull at expiry time model. No functional change.

Signed-off-by: default avatarAnna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240221090548.36600-13-anna-maria@linutronix.de
parent 21927fc8

kernel/time/timer.c

+38 −26
Original line number Diff line number Diff line
@@ -2033,30 +2033,13 @@ static unsigned long next_timer_interrupt(struct timer_base *base, 
	return base->next_expiry;

}



static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,

					     bool *idle)

static unsigned long fetch_next_timer_interrupt(unsigned long basej, u64 basem,

						struct timer_base *base_local,

						struct timer_base *base_global,

						struct timer_events *tevt)

{

	struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX };

	unsigned long nextevt, nextevt_local, nextevt_global;

	struct timer_base *base_local, *base_global;

	bool local_first;

	u64 expires;



	/*

	 * Pretend that there is no timer pending if the cpu is offline.

	 * Possible pending timers will be migrated later to an active cpu.

	 */

	if (cpu_is_offline(smp_processor_id())) {

		if (idle)

			*idle = true;

		return tevt.local;

	}



	base_local = this_cpu_ptr(&timer_bases[BASE_LOCAL]);

	base_global = this_cpu_ptr(&timer_bases[BASE_GLOBAL]);



	raw_spin_lock(&base_local->lock);

	raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);



	nextevt_local = next_timer_interrupt(base_local, basej);

	nextevt_global = next_timer_interrupt(base_global, basej);
@@ -2074,8 +2057,8 @@ static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem, 
		/* If we missed a tick already, force 0 delta */

		if (time_before(nextevt, basej))

			nextevt = basej;

		tevt.local = basem + (u64)(nextevt - basej) * TICK_NSEC;

		goto forward;

		tevt->local = basem + (u64)(nextevt - basej) * TICK_NSEC;

		return nextevt;

	}



	/*
@@ -2085,12 +2068,41 @@ static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem, 
	 * ignored. If the global queue is empty, nothing to do either.

	 */

	if (!local_first && base_global->timers_pending)

		tevt.global = basem + (u64)(nextevt_global - basej) * TICK_NSEC;

		tevt->global = basem + (u64)(nextevt_global - basej) * TICK_NSEC;



	if (base_local->timers_pending)

		tevt.local = basem + (u64)(nextevt_local - basej) * TICK_NSEC;

		tevt->local = basem + (u64)(nextevt_local - basej) * TICK_NSEC;



	return nextevt;

}



static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,

					     bool *idle)

{

	struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX };

	struct timer_base *base_local, *base_global;

	unsigned long nextevt;

	u64 expires;



	/*

	 * Pretend that there is no timer pending if the cpu is offline.

	 * Possible pending timers will be migrated later to an active cpu.

	 */

	if (cpu_is_offline(smp_processor_id())) {

		if (idle)

			*idle = true;

		return tevt.local;

	}



	base_local = this_cpu_ptr(&timer_bases[BASE_LOCAL]);

	base_global = this_cpu_ptr(&timer_bases[BASE_GLOBAL]);



	raw_spin_lock(&base_local->lock);

	raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING);



	nextevt = fetch_next_timer_interrupt(basej, basem, base_local,

					     base_global, &tevt);



forward:

	/*

	 * We have a fresh next event. Check whether we can forward the

	 * base.