Re: [PATCH 10/23] cpu: Use RCU to protect access of HK_TYPE_TIMER cpumask

Thomas Gleixner
2026-04-21T08:58:02Z

On Mon, Apr 20 2026 at 23:03, Waiman Long wrote:
> As HK_TYPE_TIMER cpumask is going to be changeable at run time, use
> RCU to protect access to the cpumask.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
> kernel/cpu.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index bc4f7a9ba64e..0d02b5d7a7ba 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1890,6 +1890,8 @@ int freeze_secondary_cpus(int primary)
> cpu_maps_update_begin();
> if (primary == -1) {
> primary = cpumask_first(cpu_online_mask);
> +
> + guard(rcu)();
> if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
> primary = housekeeping_any_cpu(HK_TYPE_TIMER);

housekeeping_cpu() and housekeeping_any_cpu() can operate on two
different CPU masks once the runtime update is enabled.

Seriously?