[PATCH v7 07/21] timers: Introduce add_timer() variants which modify timer flags

Anna-Maria Behnsen
2023-05-24T07:07:32Z

Timer might be used as pinned timer (using add_timer_on()) and later on as
non pinned timers using add_timer(). When the NOHZ timer pull at expiry
model is in place, TIMER_PINNED flag is required to be used whenever a
timer needs to expire on a dedicated CPU. Flag must no 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 reset/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>
---
New in v6
---
include/linux/timer.h | 2 ++
kernel/time/timer.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 36 insertions(+)

diff --git a/include/linux/timer.h b/include/linux/timer.h
index 9162f275819a..6f96661480dd 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -180,6 +180,8 @@ 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);
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1522fb81887e..ab9a8bb11a8a 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1242,6 +1242,40 @@ 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
--
2.30.2