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

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Message-ID: <20150217143142.GB15881@red-moon>
Date:	Tue, 17 Feb 2015 14:31:42 +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 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.

Lorenzo

> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Nicolas Pitre <nico@...aro.org>
> Cc: Russell King <rmk+kernel@....linux.org.uk>
> 
> ---
>  include/linux/tick.h      |    3 +++
>  kernel/time/tick-common.c |   18 +++++++++++++++---
>  2 files changed, 18 insertions(+), 3 deletions(-)
> 
> Index: linux/include/linux/tick.h
> ===================================================================
> --- linux.orig/include/linux/tick.h
> +++ linux/include/linux/tick.h
> @@ -27,12 +27,15 @@ extern struct tick_device *tick_get_devi
>  
>  #ifdef CONFIG_GENERIC_CLOCKEVENTS
>  extern void __init tick_init(void);
> +/* Should be core only, but arm BL switcher has its homebrewn implementation */
> +extern void tick_suspend_local(void);
>  /* Should be core only, but XEN resume magic requires this */
>  extern void tick_resume_local(void);
>  /* CPU hotplug */
>  extern void tick_shutdown_local(void);
>  #else /* CONFIG_GENERIC_CLOCKEVENTS */
>  static inline void tick_init(void) { }
> +static inline void tick_suspend_local(void) { }
>  static inline void tick_resume_local(void) { }
>  static inline void tick_shutdown_local(void) { }
>  #endif /* !CONFIG_GENERIC_CLOCKEVENTS */
> Index: linux/kernel/time/tick-common.c
> ===================================================================
> --- linux.orig/kernel/time/tick-common.c
> +++ linux/kernel/time/tick-common.c
> @@ -370,6 +370,20 @@ void tick_shutdown_local(void)
>  
>  #ifdef CONFIG_PM_SLEEP
>  /**
> + * tick_suspend_local - Suspend the local tick device
> + *
> + * Called from the local cpu for freeze with interrupts disabled.
> + *
> + * No locks required. Nothing can change the per cpu device.
> + */
> +void tick_suspend_local(void)
> +{
> +	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
> +
> +	clockevents_shutdown(td->evtdev);
> +}
> +
> +/**
>   * tick_suspend - Suspend the tick and the broadcast device
>   *
>   * Called from syscore_suspend() via timekeeping_suspend with only one
> @@ -379,9 +393,7 @@ void tick_shutdown_local(void)
>   */
>  void tick_suspend(void)
>  {
> -	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
> -
> -	clockevents_shutdown(td->evtdev);
> +	tick_suspend_local();
>  	tick_suspend_broadcast();
>  }
>  
> 
> 
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