Subject: Re: [PATCH 25/36] time/tick-broadcast: Remove RCU_NONIDLE usage

From: Mark Rutland <[email-masked]>
Date: Tue, 14 Jun 2022 17:28:02 +0100

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On Wed, Jun 08, 2022 at 04:27:48PM +0200, Peter Zijlstra wrote:
> No callers left that have already disabled RCU.
> 
> Signed-off-by: Peter Zijlstra (Intel) <[email-masked]>

Acked-by: Mark Rutland <[email-masked]>

Mark.

> ---
>  kernel/time/tick-broadcast-hrtimer.c |   29 ++++++++++++-----------------
>  1 file changed, 12 insertions(+), 17 deletions(-)
> 
> --- a/kernel/time/tick-broadcast-hrtimer.c
> +++ b/kernel/time/tick-broadcast-hrtimer.c
> @@ -56,25 +56,20 @@ static int bc_set_next(ktime_t expires,
>  	 * hrtimer callback function is currently running, then
>  	 * hrtimer_start() cannot move it and the timer stays on the CPU on
>  	 * which it is assigned at the moment.
> +	 */
> +	hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED_HARD);
> +	/*
> +	 * The core tick broadcast mode expects bc->bound_on to be set
> +	 * correctly to prevent a CPU which has the broadcast hrtimer
> +	 * armed from going deep idle.
>  	 *
> -	 * As this can be called from idle code, the hrtimer_start()
> -	 * invocation has to be wrapped with RCU_NONIDLE() as
> -	 * hrtimer_start() can call into tracing.
> +	 * As tick_broadcast_lock is held, nothing can change the cpu
> +	 * base which was just established in hrtimer_start() above. So
> +	 * the below access is safe even without holding the hrtimer
> +	 * base lock.
>  	 */
> -	RCU_NONIDLE( {
> -		hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED_HARD);
> -		/*
> -		 * The core tick broadcast mode expects bc->bound_on to be set
> -		 * correctly to prevent a CPU which has the broadcast hrtimer
> -		 * armed from going deep idle.
> -		 *
> -		 * As tick_broadcast_lock is held, nothing can change the cpu
> -		 * base which was just established in hrtimer_start() above. So
> -		 * the below access is safe even without holding the hrtimer
> -		 * base lock.
> -		 */
> -		bc->bound_on = bctimer.base->cpu_base->cpu;
> -	} );
> +	bc->bound_on = bctimer.base->cpu_base->cpu;
> +
>  	return 0;
>  }
>  
> 
>