Re: [PATCH 1/3] sched/isolation: Add HK_FLAG_SCHED to nohz_full

[Frederic Weisbecker <frederic@kernel.org>]

Le Sun, Aug 18, 2024 at 07:45:18PM -0400, Waiman Long a écrit :
> The HK_FLAG_SCHED/HK_TYPE_SCHED flag is defined and is also used
> in kernel/sched/fair.c since commit de201559df87 ("sched/isolation:
> Introduce housekeeping flags"). However, the corresponding cpumask isn't
> currently updated anywhere. So the mask is always cpu_possible_mask.
> 
> Add it in nohz_full setup so that nohz_full CPUs will now be removed
> from HK_TYPE_SCHED cpumask.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>  kernel/sched/isolation.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
> index 5891e715f00d..a514994af319 100644
> --- a/kernel/sched/isolation.c
> +++ b/kernel/sched/isolation.c
> @@ -196,7 +196,7 @@ static int __init housekeeping_nohz_full_setup(char *str)
>  	unsigned long flags;
>  
>  	flags = HK_FLAG_TICK | HK_FLAG_WQ | HK_FLAG_TIMER | HK_FLAG_RCU |
> -		HK_FLAG_MISC | HK_FLAG_KTHREAD;
> +		HK_FLAG_MISC | HK_FLAG_KTHREAD | HK_FLAG_SCHED;
>  
>  	return housekeeping_setup(str, flags);
>  }

find_new_ilb() already has HK_FLAG_MISC to prevent an isolated CPU
from being elected as an ilb. So I think we should simply remove HK_FLAG_SCHED.

Thanks.