Re: [PATCH v5 14/18] timer: Check if timers base is handled already

Peter Zijlstra
2023-03-21T14:44:17Z

On Wed, Mar 01, 2023 at 03:17:40PM +0100, Anna-Maria Behnsen wrote:
> Due to the conversion of the NOHZ timer placement to a pull at expiry
> time model, the per CPU timer bases with non pinned timers are no
> longer handled only by the local CPU. In case a remote CPU already
> expires the non pinned timers base of the local cpu, nothing more
> needs to be done by the local CPU. A check at the begin of the expire
> timers routine is required, because timer base lock is dropped before
> executing the timer callback function.
>
> This is a preparatory work, but has no functional impact right now.
>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
> ---
> kernel/time/timer.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index be085e94afcc..9553da99e262 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -2144,6 +2144,9 @@ static inline void __run_timers(struct timer_base *base)
>
> lockdep_assert_held(&base->lock);
>
> + if (!!base->running_timer)
> + return;

You can leave out the double-negation, 'if (base->running_timer)' is
equivalent and reads much easier.

> while (time_after_eq(jiffies, base->clk) &&
> time_after_eq(jiffies, base->next_expiry)) {
> levels = collect_expired_timers(base, heads);
> --
> 2.30.2
>