linux-kernel - Re: [PATCH 34/35] tick: Provide tick_suspend

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Date:	Wed, 18 Feb 2015 16:38:27 +0000
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	Nicolas Pitre <nico@...aro.org>,
	Russell King <rmk+kernel@....linux.org.uk>
Subject: Re: [PATCH 34/35] tick: Provide tick_suspend_local()

On Wed, Feb 18, 2015 at 01:35:24PM +0000, Peter Zijlstra wrote:
> On Tue, Feb 17, 2015 at 02:31:42PM +0000, Lorenzo Pieralisi wrote:
> > On Mon, Feb 16, 2015 at 12:15:09PM +0000, Peter Zijlstra wrote:
> > > From: Thomas Gleixner <tglx@...utronix.de>
> > > 
> > > This function is intended to use by the freezer once the freezer folks
> > > solved their race issues. Also required to get rid of the ARM BL
> > > switcher tick hackery.
> > 
> > Totally agree with the patch(es), but I noticed that the ARM bL switcher
> > does not depend on PM_SLEEP, so I do not think you can compile
> > tick_{suspend/resume}_local() out if !PM_SLEEP, unless dependency
> > is enforced by the ARM bL switcher config but I do not think that
> > the config dependency really exists, Nico please correct me if I am
> > wrong.
> 
> Ah I see, the headers seem to do the right thing and declare the
> function in core (GENERIC_CLOCKEVENTS) with a comment.
> 
> But then the patch continues defining the functions under PM_SLEEP.
> 
> I wonder why the build robot has not reported fail on this..
> 
> Would the below make sense?

Yes, but please see Rafael's remark, whatever makes it easier for you.

Thanks,
Lorenzo

> 
> ---
> --- a/kernel/time/tick-common.c
> +++ b/kernel/time/tick-common.c
> @@ -368,7 +368,6 @@ void tick_shutdown_local(void)
>  }
>  #endif
>  
> -#ifdef CONFIG_PM_SLEEP
>  /**
>   * tick_suspend_local - Suspend the local tick device
>   *
> @@ -384,20 +383,6 @@ void tick_suspend_local(void)
>  }
>  
>  /**
> - * tick_suspend - Suspend the tick and the broadcast device
> - *
> - * Called from syscore_suspend() via timekeeping_suspend with only one
> - * CPU online and interrupts disabled.
> - *
> - * No locks required. Nothing can change the per cpu device.
> - */
> -void tick_suspend(void)
> -{
> -	tick_suspend_local();
> -	tick_suspend_broadcast();
> -}
> -
> -/**
>   * tick_resume_local - Resume the local tick device
>   *
>   * Called from the local cpu for unfreeze or XEN resume magic
> @@ -418,6 +403,21 @@ void tick_resume_local(void)
>  	}
>  }
>  
> +#ifdef CONFIG_PM_SLEEP
> +/**
> + * tick_suspend - Suspend the tick and the broadcast device
> + *
> + * Called from syscore_suspend() via timekeeping_suspend with only one
> + * CPU online and interrupts disabled.
> + *
> + * No locks required. Nothing can change the per cpu device.
> + */
> +void tick_suspend(void)
> +{
> +	tick_suspend_local();
> +	tick_suspend_broadcast();
> +}
> +
>  /**
>   * tick_resume - Resume the tick and the broadcast device
>   *
> 
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