linux-kernel - Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier transitions

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Message-ID: <57050A98.80901@cantab.net>
Date:	Wed, 6 Apr 2016 14:09:44 +0100
From:	David Vrabel <dvrabel@...tab.net>
To:	Anna-Maria Gleixner <anna-maria@...utronix.de>,
	linux-kernel@...r.kernel.org
Cc:	xen-devel@...ts.xenproject.org,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	rt@...utronix.de, David Vrabel <david.vrabel@...rix.com>
Subject: Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier
 transitions

On 04/04/16 13:32, Anna-Maria Gleixner wrote:
> Xen guests do not offline/online CPUs during suspend/resume and
> therefore FROZEN notifier transitions are not required. Add this
> explanation as a comment in the code to get not confused why
> CPU_TASKS_FROZEN masked transitions are not considered.
> 
> Cc: David Vrabel <david.vrabel@...rix.com>
> Cc: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Cc: xen-devel@...ts.xenproject.org 
> Signed-off-by: Anna-Maria Gleixner <anna-maria@...utronix.de>
> ---
>  arch/arm/xen/enlighten.c         |    6 ++++++
>  arch/x86/xen/enlighten.c         |    7 +++++++
>  drivers/xen/events/events_fifo.c |    6 ++++++
>  3 files changed, 19 insertions(+)
> 
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -213,6 +213,12 @@ static int xen_cpu_notification(struct n
>  				unsigned long action,
>  				void *hcpu)
>  {
> +	/*
> +	 * Xen guests do not offline/online CPUs during
> +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> +	 * are not considered.
> +	 */

This may not be true for arm guests.

David