[PATCH] tick/sched: Drop duplicated tick_sched.inidle

[PATCH] tick/sched: Drop duplicated tick_sched.inidle

[Peter Xu]

It is set before entering idle and cleared when quitting idle, though
it seems to be a complete duplicate of tick_sched.idle_active.  We
should probably be able to use any one of them to replace the other.

CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@kernel.org>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 kernel/time/tick-sched.c | 11 ++++-------
 kernel/time/tick-sched.h |  3 +--
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f4ee1a3428ae..6bb5ad03e962 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -137,7 +137,7 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
 	if (tick_do_timer_cpu == cpu)
 		tick_do_update_jiffies64(now);
 
-	if (ts->inidle)
+	if (ts->idle_active)
 		ts->got_idle_tick = 1;
 }
 
@@ -534,7 +534,6 @@ static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
 {
 	update_ts_time_stats(smp_processor_id(), ts, now, NULL);
 	ts->idle_active = 0;
-
 	sched_clock_idle_wakeup_event();
 }
 
@@ -999,7 +998,6 @@ void tick_nohz_idle_enter(void)
 
 	WARN_ON_ONCE(ts->timer_expires_base);
 
-	ts->inidle = 1;
 	tick_nohz_start_idle(ts);
 
 	local_irq_enable();
@@ -1017,7 +1015,7 @@ void tick_nohz_irq_exit(void)
 {
 	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
 
-	if (ts->inidle)
+	if (ts->idle_active)
 		tick_nohz_start_idle(ts);
 	else
 		tick_nohz_full_update_tick(ts);
@@ -1067,7 +1065,7 @@ ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
 	ktime_t now = ts->idle_entrytime;
 	ktime_t next_event;
 
-	WARN_ON_ONCE(!ts->inidle);
+	WARN_ON_ONCE(!ts->idle_active);
 
 	*delta_next = ktime_sub(dev->next_event, now);
 
@@ -1163,10 +1161,9 @@ void tick_nohz_idle_exit(void)
 
 	local_irq_disable();
 
-	WARN_ON_ONCE(!ts->inidle);
+	WARN_ON_ONCE(!ts->idle_active);
 	WARN_ON_ONCE(ts->timer_expires_base);
 
-	ts->inidle = 0;
 	idle_active = ts->idle_active;
 	tick_stopped = ts->tick_stopped;
 
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 4fb06527cf64..ae9335d019f0 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -31,7 +31,7 @@ enum tick_nohz_mode {
  * @idle_active:	Indicator that the CPU is actively in the tick idle mode;
  *			it is resetted during irq handling phases.
  * @do_timer_lst:	CPU was the last one doing do_timer before going idle
- * @got_idle_tick:	Tick timer function has run with @inidle set
+ * @got_idle_tick:	Tick timer function has run with @idle_active set
  * @last_tick:		Store the last tick expiry time when the tick
  *			timer is modified for nohz sleeps. This is necessary
  *			to resume the tick timer operation in the timeline
@@ -55,7 +55,6 @@ struct tick_sched {
 	unsigned long			check_clocks;
 	enum tick_nohz_mode		nohz_mode;
 
-	unsigned int			inidle		: 1;
 	unsigned int			tick_stopped	: 1;
 	unsigned int			idle_active	: 1;
 	unsigned int			do_timer_last	: 1;
-- 
2.17.1

Re: [PATCH] tick/sched: Drop duplicated tick_sched.inidle

[Frederic Weisbecker]

On Wed, May 22, 2019 at 11:29:06AM +0800, Peter Xu wrote:
> It is set before entering idle and cleared when quitting idle, though
> it seems to be a complete duplicate of tick_sched.idle_active.  We
> should probably be able to use any one of them to replace the other.

Not exactly.

@inidle is set on idle entry and cleared on idle exit.
@idle_active is the same but it's cleared during idle interrupts
so that idle_sleeptime only account real idle time.

And note below:

> @@ -1017,7 +1015,7 @@ void tick_nohz_irq_exit(void)
>  {
>  	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
>  
> -	if (ts->inidle)
> +	if (ts->idle_active)
>  		tick_nohz_start_idle(ts);

idle_active will always be cleared here from tick_nohz_irq_enter().
We actually want to conditionally set it again depending on the inidle value.

Thanks.

Re: [PATCH] tick/sched: Drop duplicated tick_sched.inidle

[Peter Xu]

On Wed, May 22, 2019 at 02:18:41PM +0200, Frederic Weisbecker wrote:
> On Wed, May 22, 2019 at 11:29:06AM +0800, Peter Xu wrote:
> > It is set before entering idle and cleared when quitting idle, though
> > it seems to be a complete duplicate of tick_sched.idle_active.  We
> > should probably be able to use any one of them to replace the other.
> 
> Not exactly.
> 
> @inidle is set on idle entry and cleared on idle exit.
> @idle_active is the same but it's cleared during idle interrupts
> so that idle_sleeptime only account real idle time.
> 
> And note below:
> 
> > @@ -1017,7 +1015,7 @@ void tick_nohz_irq_exit(void)
> >  {
> >  	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
> >  
> > -	if (ts->inidle)
> > +	if (ts->idle_active)
> >  		tick_nohz_start_idle(ts);
> 
> idle_active will always be cleared here from tick_nohz_irq_enter().
> We actually want to conditionally set it again depending on the inidle value.

You are right; I've missed the calls from irq enter/exit. Thanks, Frederic.

-- 
Peter Xu