[tip: timers/core] hrtimer: Select housekeeping CPU during migration

[tip-bot2 for Costa Shulyupin]

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

Commit-ID:     86342554e102b0d18d50abec43d40f4fc92f1993
Gitweb:        https://git.kernel.org/tip/86342554e102b0d18d50abec43d40f4fc92f1993
Author:        Costa Shulyupin <costa.shul@xxxxxxxxxx>
AuthorDate:    Tue, 13 Feb 2024 18:46:51 +02:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 13 Feb 2024 20:44:14 +01:00

hrtimer: Select housekeeping CPU during migration

During CPU-down hotplug, hrtimers may migrate to isolated CPUs,
compromising CPU isolation.

Address 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>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
Reviewed-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240213164650.2935909-3-costa.shul@xxxxxxxxxx
---
 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 7607939..438208a 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2221,8 +2221,8 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 
 int hrtimers_cpu_dying(unsigned int dying_cpu)
 {
+	int i, ncpu = cpumask_any_and(cpu_active_mask, housekeeping(HK_TYPE_TIMER));
 	struct hrtimer_cpu_base *old_base, *new_base;
-	int i, ncpu = cpumask_first(cpu_active_mask);
 
 	tick_cancel_sched_timer(dying_cpu);