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timers: Introduce add_timer() variants which modify timer flags

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A timer might be used as a pinned timer (using add_timer_on()) and later on
as non-pinned timer using add_timer(). When the "NOHZ timer pull at expiry
model" is in place, the TIMER_PINNED flag is required to be used whenever a
timer needs to expire on a dedicated CPU. Otherwise the flag must not be
set if expiration on a dedicated CPU is not required.

add_timer_on()'s behavior will be changed during the preparation patches
for the "NOHZ timer pull at expiry model" to unconditionally set the
TIMER_PINNED flag. To be able to clear/ set the flag when queueing a
timer, two variants of add_timer() are introduced.

This is a preparatory step and has 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/20240221090548.36600-6-anna-maria@linutronix.de
This commit is contained in:
Anna-Maria Behnsen 2024-02-21 10:05:33 +01:00 committed by Thomas Gleixner
parent 73129cf4b6
commit 8e7e247f64
2 changed files with 36 additions and 0 deletions
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2
include/linux/timer.h
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@ -165,6 +165,8 @@ extern int timer_reduce(struct timer_list *timer, unsigned long expires);
#define NEXT_TIMER_MAX_DELTA ((1UL << 30) - 1)
extern void add_timer(struct timer_list *timer);
extern void add_timer_local(struct timer_list *timer);
extern void add_timer_global(struct timer_list *timer);
extern int try_to_del_timer_sync(struct timer_list *timer);
extern int timer_delete_sync(struct timer_list *timer);

34
kernel/time/timer.c
View File

@ -1290,6 +1290,40 @@ void add_timer(struct timer_list *timer)
}
EXPORT_SYMBOL(add_timer);
/**
* add_timer_local() - Start a timer on the local CPU
* @timer: The timer to be started
*
* Same as add_timer() except that the timer flag TIMER_PINNED is set.
*
* See add_timer() for further details.
*/
void add_timer_local(struct timer_list *timer)
{
if (WARN_ON_ONCE(timer_pending(timer)))
return;
timer->flags |= TIMER_PINNED;
__mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
}
EXPORT_SYMBOL(add_timer_local);
/**
* add_timer_global() - Start a timer without TIMER_PINNED flag set
* @timer: The timer to be started
*
* Same as add_timer() except that the timer flag TIMER_PINNED is unset.
*
* See add_timer() for further details.
*/
void add_timer_global(struct timer_list *timer)
{
if (WARN_ON_ONCE(timer_pending(timer)))
return;
timer->flags &= ~TIMER_PINNED;
__mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING);
}
EXPORT_SYMBOL(add_timer_global);
/**
* add_timer_on - Start a timer on a particular CPU
* @timer: The timer to be started