Commit 8e7e247f authored by Anna-Maria Behnsen's avatar Anna-Maria Behnsen Committed by Thomas Gleixner
Browse files

timers: Introduce add_timer() variants which modify timer flags 



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: 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/20240221090548.36600-6-anna-maria@linutronix.de
parent 73129cf4

include/linux/timer.h

+2 −0
Original line number Diff line number Diff line
@@ -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);

kernel/time/timer.c

+34 −0
Original line number Diff line number Diff line
@@ -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