Re: [PATCH v9 07/10] time: hrtimer: Introduce hrtimer_next_event_without()

Rafael J. Wysocki
2018-04-08T08:20:25Z

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@intel.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@intel.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@intel.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@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
kernel/time/hrtimer.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)

Index: linux-pm/kernel/time/hrtimer.c
===================================================================
--- linux-pm.orig/kernel/time/hrtimer.c
+++ linux-pm/kernel/time/hrtimer.c
@@ -505,9 +505,7 @@ static ktime_t __hrtimer_next_event_base
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);
+ next = timerqueue_iterate_next(next);
if (!next)
continue;