Re: [PATCH 1/9] timer: Move trigger_dyntick_cpu() to enqueue_timer()

Anna-Maria Behnsen
2020-07-09T12:17:40Z

Hi Frederic,

On Tue, 7 Jul 2020, Frederic Weisbecker wrote:

> Consolidate the code by calling trigger_dyntick_cpu() from
> enqueue_timer() instead of calling it from all its callers.

Looks good, but maybe you could also update the comments in the code (see
remarks below)?

> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> ---
> kernel/time/timer.c | 46 +++++++++++++++++++--------------------------
> 1 file changed, 19 insertions(+), 27 deletions(-)
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 9a838d38dbe6..4c977df3610b 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -596,13 +573,29 @@ trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
> wake_up_nohz_cpu(base->cpu);
> }
>
> -static void
> -internal_add_timer(struct timer_base *base, struct timer_list *timer)
> +/*
> + * Enqueue the timer into the hash bucket, mark it pending in
> + * the bitmap and store the index in the timer flags.
> + */

enqueue_timer() also calls trigger_dyntick_cpu().

> +static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
> + unsigned int idx)
> {
> - __internal_add_timer(base, timer);
> + hlist_add_head(&timer->entry, base->vectors + idx);
> + __set_bit(idx, base->pending_map);
> + timer_set_idx(timer, idx);
> +
> + trace_timer_start(timer, timer->expires, timer->flags);
> trigger_dyntick_cpu(base, timer);
> }
>
> +static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
> +{
> + unsigned int idx;
> +
> + idx = calc_wheel_index(timer->expires, base->clk);
> + enqueue_timer(base, timer, idx);
> +}
> +
> #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
>
> static struct debug_obj_descr timer_debug_descr;
> @@ -1059,7 +1052,6 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option
> */

The comment above still mentions that trigger_dyntick_cpu() is called which
is now part of enqueue_timer(). Might be a little confusing.

> if (idx != UINT_MAX && clk == base->clk) {
> enqueue_timer(base, timer, idx);
> - trigger_dyntick_cpu(base, timer);
> } else {
> internal_add_timer(base, timer);
> }

Thanks,

Anna-Maria