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

[Mark Rutland <mark.rutland@xxxxxxx>]

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) <peterz@xxxxxxxxxxxxx>

Acked-by: Mark Rutland <mark.rutland@xxxxxxx>

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;
>  }
>  
> 
>