linux-kernel - Re: [PATCH v9 07/10] time: hrtimer: Introduce hrtimer_next_event

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Message-ID: <20180407144637.GC16600@lerouge>
Date:   Sat, 7 Apr 2018 16:46:38 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Thomas Ilsche <thomas.ilsche@...dresden.de>,
        Doug Smythies <dsmythies@...us.net>,
        Rik van Riel <riel@...riel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Mike Galbraith <mgalbraith@...e.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>
Subject: Re: [PATCH v9 07/10] time: hrtimer: Introduce
 hrtimer_next_event_without()

On Wed, Apr 04, 2018 at 10:45:39AM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The next set of changes will need to compute the time to the next
> hrtimer event over all hrtimers except for the scheduler tick one.
> 
> To that end introduce a new helper function,
> hrtimer_next_event_without(), for computing the time until the next
> hrtimer event over all timers except for one and modify the underlying
> code in __hrtimer_next_event_base() to prepare it for being called by
> that new function.
> 
> No intentional changes in functionality.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> v8 -> v9:
>  * Make fewer changes to the existing code.
>  * Add a new helper function for the handling of the use case at hand.
> 
> ---
>  include/linux/hrtimer.h |    1 
>  kernel/time/hrtimer.c   |   55 ++++++++++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 54 insertions(+), 2 deletions(-)
> 
> Index: linux-pm/include/linux/hrtimer.h
> ===================================================================
> --- linux-pm.orig/include/linux/hrtimer.h
> +++ linux-pm/include/linux/hrtimer.h
> @@ -426,6 +426,7 @@ static inline ktime_t hrtimer_get_remain
>  }
>  
>  extern u64 hrtimer_get_next_event(void);
> +extern u64 hrtimer_next_event_without(const struct hrtimer *exclude);
>  
>  extern bool hrtimer_active(const struct hrtimer *timer);
>  
> Index: linux-pm/kernel/time/hrtimer.c
> ===================================================================
> --- linux-pm.orig/kernel/time/hrtimer.c
> +++ linux-pm/kernel/time/hrtimer.c
> @@ -490,6 +490,7 @@ __next_base(struct hrtimer_cpu_base *cpu
>  	while ((base = __next_base((cpu_base), &(active))))
>  
>  static ktime_t __hrtimer_next_event_base(struct hrtimer_cpu_base *cpu_base,
> +					 const struct hrtimer *exclude,
>  					 unsigned int active,
>  					 ktime_t expires_next)
>  {
> @@ -502,9 +503,24 @@ static ktime_t __hrtimer_next_event_base
>  
>  		next = timerqueue_getnext(&base->active);
>  		timer = container_of(next, struct hrtimer, node);
> +		if (timer == exclude) {
> +			/* Get to the next timer in the queue. */
> +			struct rb_node *rbn = rb_next(&next->node);
> +
> +			next = rb_entry_safe(rbn, struct timerqueue_node, node);
> +			if (!next)
> +				continue;

Minor cosmectic detail again, timerqueue_iterate_next() would do the job and
avoid browsing timerqueue details.

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>

Thanks.