[tip: timers/core] timers: Make sure TIMER_PINNED flag is set in add_timer_on()

[tip-bot2 for Anna-Maria Behnsen]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     aae55e9fb8fc73893f86165f0d84a33b7080902a
Gitweb:        https://git.kernel.org/tip/aae55e9fb8fc73893f86165f0d84a33b7080902a
Author:        Anna-Maria Behnsen <anna-maria@xxxxxxxxxxxxx>
AuthorDate:    Wed, 21 Feb 2024 10:05:35 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Thu, 22 Feb 2024 17:52:31 +01:00

timers: Make sure TIMER_PINNED flag is set in add_timer_on()

When adding a timer to the timer wheel using add_timer_on(), it is an
implicitly pinned timer. With the timer pull at expiry time model in place,
the TIMER_PINNED flag is required to make sure timers end up in proper
base.

Set the TIMER_PINNED flag unconditionally when add_timer_on() is executed.

Signed-off-by: Anna-Maria Behnsen <anna-maria@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240221090548.36600-8-anna-maria@xxxxxxxxxxxxx

---
 kernel/time/timer.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index bef8cb8..121f5b9 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1329,7 +1329,10 @@ EXPORT_SYMBOL(add_timer_global);
  * @timer:	The timer to be started
  * @cpu:	The CPU to start it on
  *
- * Same as add_timer() except that it starts the timer on the given CPU.
+ * Same as add_timer() except that it starts the timer on the given CPU and
+ * the TIMER_PINNED flag is set. When timer shouldn't be a pinned timer in
+ * the next round, add_timer_global() should be used instead as it unsets
+ * the TIMER_PINNED flag.
  *
  * See add_timer() for further details.
  */
@@ -1343,6 +1346,9 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	if (WARN_ON_ONCE(timer_pending(timer)))
 		return;
 
+	/* Make sure timer flags have TIMER_PINNED flag set */
+	timer->flags |= TIMER_PINNED;
+
 	new_base = get_timer_cpu_base(timer->flags, cpu);
 
 	/*