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

Mark Rutland
2022-06-14T16:29:18Z

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@infradead.org>

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

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;
> }
>
>
>