[v10,05/20] timers: Introduce add_timer() variants which modify timer flags
Commit Message
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
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 patch and has no functional change.
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
v10: Commit message reworded as suggested by bigeasy
v9: Update documentation to match kernel-doc style (missing brackets after
function names)
New in v6
---
include/linux/timer.h | 2 ++
kernel/time/timer.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)
Comments
Le Mon, Jan 15, 2024 at 03:37:28PM +0100, Anna-Maria Behnsen a écrit :
> timer flags
Yes ;-)
>
> 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
> 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 patch and has no functional change.
>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Frederic Weisbecker <frederic@kernel.org> writes:
> Le Mon, Jan 15, 2024 at 03:37:28PM +0100, Anna-Maria Behnsen a écrit :
>> timer flags
>
> Yes ;-)
Something got broken when importing the quilt series into git... This
also happend to some other patches/commit messages. I'll have a look at
it and will fix it.
Thanks,
Anna-Maria
@@ -179,6 +179,8 @@ 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);
@@ -1245,6 +1245,40 @@ 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