[PATCH v2] hrtimer: select housekeeping CPU during migration

[Costa Shulyupin]

During CPU-down hotplug, hrtimers may migrate to isolated CPUs,
compromising CPU isolation. This commit addresses this issue by
masking valid CPUs for hrtimers using housekeeping_cpumask(HK_TYPE_TIMER).

Suggested-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Costa Shulyupin <costa.shul@xxxxxxxxxx>
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
---

Changes in v2:
- [v1] https://lore.kernel.org/all/20240211135213.2518068-1-costa.shul@xxxxxxxxxx/
- reworded and rebased on linux-next
---
 kernel/time/hrtimer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index edb0f821dcea..947bd6cf7105 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2224,7 +2224,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 int hrtimers_cpu_dying(unsigned int dying_cpu)
 {
 	struct hrtimer_cpu_base *old_base, *new_base;
-	int i, ncpu = cpumask_first(cpu_active_mask);
+	int i, ncpu = cpumask_any_and(cpu_active_mask, housekeeping(HK_TYPE_TIMER));
 
 	tick_cancel_sched_timer(dying_cpu);
 
-- 
2.43.0