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timers: Split out "get next timer interrupt" functionality

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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: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20240221090548.36600-13-anna-maria@linutronix.de
This commit is contained in:
Anna-Maria Behnsen 2024-02-21 10:05:40 +01:00 committed by Thomas Gleixner
parent 21927fc89e
commit 70b4cf84f3
1 changed files with 46 additions and 34 deletions
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80
kernel/time/timer.c
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@ -2033,13 +2033,55 @@ static unsigned long next_timer_interrupt(struct timer_base *base,
return base->next_expiry;
}
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)
{
unsigned long nextevt, nextevt_local, nextevt_global;
bool local_first;
nextevt_local = next_timer_interrupt(base_local, basej);
nextevt_global = next_timer_interrupt(base_global, basej);
local_first = time_before_eq(nextevt_local, nextevt_global);
nextevt = local_first ? nextevt_local : nextevt_global;
/*
* If the @nextevt is at max. one tick away, use @nextevt and store
* it in the local expiry value. The next global event is irrelevant in
* this case and can be left as KTIME_MAX.
*/
if (time_before_eq(nextevt, basej + 1)) {
/* If we missed a tick already, force 0 delta */
if (time_before(nextevt, basej))
nextevt = basej;
tevt->local = basem + (u64)(nextevt - basej) * TICK_NSEC;
return nextevt;
}
/*
* Update tevt.* values:
*
* If the local queue expires first, then the global event can be
* 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;
if (base_local->timers_pending)
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 };
unsigned long nextevt, nextevt_local, nextevt_global;
struct timer_base *base_local, *base_global;
bool local_first;
unsigned long nextevt;
u64 expires;
/*
@ -2058,39 +2100,9 @@ static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem,
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);
nextevt = fetch_next_timer_interrupt(basej, basem, base_local,
base_global, &tevt);
local_first = time_before_eq(nextevt_local, nextevt_global);
nextevt = local_first ? nextevt_local : nextevt_global;
/*
* If the @nextevt is at max. one tick away, use @nextevt and store
* it in the local expiry value. The next global event is irrelevant in
* this case and can be left as KTIME_MAX.
*/
if (time_before_eq(nextevt, basej + 1)) {
/* 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;
}
/*
* Update tevt.* values:
*
* If the local queue expires first, then the global event can be
* 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;
if (base_local->timers_pending)
tevt.local = basem + (u64)(nextevt_local - basej) * TICK_NSEC;
forward:
/*
* We have a fresh next event. Check whether we can forward the
* base.