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

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Message-ID: <20180408175847.GA21904@lerouge>
Date:   Sun, 8 Apr 2018 19:58:48 +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 Sun, Apr 08, 2018 at 10:20:30AM +0200, Rafael J. Wysocki wrote:
> On Saturday, April 7, 2018 4:46:38 PM CEST Frederic Weisbecker wrote:
> > 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.
> 
> And below is a patch to make this change on top of the original.
> 
> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: [PATCH] time: hrtimer: Use timerqueue_iterate_next() to get to the next timer
> 
> Use timerqueue_iterate_next() to get to the next timer in
> __hrtimer_next_event_base() without browsing the timerqueue
> details diredctly.
> 
> No intentional changes in functionality.
> 
> Suggested-by: Frederic Weisbecker <frederic@...nel.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Thanks!