[PATCH] nohz: Remove ts->inidle checks before restarting the tick

[PATCH] nohz: Remove ts->inidle checks before restarting the tick

[Frederic Weisbecker]

ts->inidle is set by tick_nohz_stop_sched_tick(1) and unset
by tick_nohz_restart_sched_tick(). These two calls are assumed
to be always paired. This means that by the time we call
tick_nohz_restart_sched_tick(), ts->inidle is supposed to
be always set to 1.

Remove the checks for ts->inidle in tick_nohz_restart_sched_tick().
This simplifies a bit the code and improves its debuggability
(ie: ensure the call is paired with a tick_nohz_stop_sched_tick() call).

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
---
 kernel/time/tick-sched.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4042064..0f7c5e5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -529,20 +529,22 @@ void tick_nohz_restart_sched_tick(void)
 	ktime_t now;
 
 	local_irq_disable();
-	if (ts->idle_active || (ts->inidle && ts->tick_stopped))
+
+	WARN_ON_ONCE(!ts->inidle);
+
+	ts->inidle = 0;
+
+	if (ts->idle_active || ts->tick_stopped)
 		now = ktime_get();
 
 	if (ts->idle_active)
 		tick_nohz_stop_idle(cpu, now);
 
-	if (!ts->inidle || !ts->tick_stopped) {
-		ts->inidle = 0;
+	if (!ts->tick_stopped) {
 		local_irq_enable();
 		return;
 	}
 
-	ts->inidle = 0;
-
 	rcu_exit_nohz();
 
 	/* Update jiffies first */
-- 
1.7.5.4

Re: [PATCH] nohz: Remove ts->inidle checks before restarting the tick

[Yong Zhang]

On Tue, Dec 06, 2011 at 03:30:43PM +0100, Frederic Weisbecker wrote:
> ts->inidle is set by tick_nohz_stop_sched_tick(1) and unset
> by tick_nohz_restart_sched_tick(). These two calls are assumed
> to be always paired. This means that by the time we call
> tick_nohz_restart_sched_tick(), ts->inidle is supposed to
> be always set to 1.
> 
> Remove the checks for ts->inidle in tick_nohz_restart_sched_tick().
> This simplifies a bit the code and improves its debuggability
> (ie: ensure the call is paired with a tick_nohz_stop_sched_tick() call).
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Reviewed-by: Yong Zhang <yong.zhang0@gmail.com>

Thanks,
Yong


> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
>  kernel/time/tick-sched.c |   12 +++++++-----
>  1 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index 4042064..0f7c5e5 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -529,20 +529,22 @@ void tick_nohz_restart_sched_tick(void)
>  	ktime_t now;
>  
>  	local_irq_disable();
> -	if (ts->idle_active || (ts->inidle && ts->tick_stopped))
> +
> +	WARN_ON_ONCE(!ts->inidle);
> +
> +	ts->inidle = 0;
> +
> +	if (ts->idle_active || ts->tick_stopped)
>  		now = ktime_get();
>  
>  	if (ts->idle_active)
>  		tick_nohz_stop_idle(cpu, now);
>  
> -	if (!ts->inidle || !ts->tick_stopped) {
> -		ts->inidle = 0;
> +	if (!ts->tick_stopped) {
>  		local_irq_enable();
>  		return;
>  	}
>  
> -	ts->inidle = 0;
> -
>  	rcu_exit_nohz();
>  
>  	/* Update jiffies first */
> -- 
> 1.7.5.4
> 
> --
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Re: [PATCH] nohz: Remove ts->inidle checks before restarting the tick

[Frederic Weisbecker]

Hi,

Just a ping to prevent this from being buried by the holidays :)

Thanks.

On Tue, Dec 06, 2011 at 03:30:43PM +0100, Frederic Weisbecker wrote:
> ts->inidle is set by tick_nohz_stop_sched_tick(1) and unset
> by tick_nohz_restart_sched_tick(). These two calls are assumed
> to be always paired. This means that by the time we call
> tick_nohz_restart_sched_tick(), ts->inidle is supposed to
> be always set to 1.
> 
> Remove the checks for ts->inidle in tick_nohz_restart_sched_tick().
> This simplifies a bit the code and improves its debuggability
> (ie: ensure the call is paired with a tick_nohz_stop_sched_tick() call).
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
>  kernel/time/tick-sched.c |   12 +++++++-----
>  1 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index 4042064..0f7c5e5 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -529,20 +529,22 @@ void tick_nohz_restart_sched_tick(void)
>  	ktime_t now;
>  
>  	local_irq_disable();
> -	if (ts->idle_active || (ts->inidle && ts->tick_stopped))
> +
> +	WARN_ON_ONCE(!ts->inidle);
> +
> +	ts->inidle = 0;
> +
> +	if (ts->idle_active || ts->tick_stopped)
>  		now = ktime_get();
>  
>  	if (ts->idle_active)
>  		tick_nohz_stop_idle(cpu, now);
>  
> -	if (!ts->inidle || !ts->tick_stopped) {
> -		ts->inidle = 0;
> +	if (!ts->tick_stopped) {
>  		local_irq_enable();
>  		return;
>  	}
>  
> -	ts->inidle = 0;
> -
>  	rcu_exit_nohz();
>  
>  	/* Update jiffies first */
> -- 
> 1.7.5.4
>