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Subject: Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier
 transitions
To: Anna-Maria Gleixner <anna-maria@linutronix.de>,
        linux-kernel@vger.kernel.org
References: <1459773140-43707-1-git-send-email-anna-maria@linutronix.de>
Cc: xen-devel@lists.xenproject.org, rt@linutronix.de,
        David Vrabel <david.vrabel@citrix.com>, sstabellini@kernel.org
From: Julien Grall <julien.grall@arm.com>
Message-ID: <57029499.7070007@arm.com>
Date: Mon, 4 Apr 2016 17:21:45 +0100
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(CC Stefano new e-mail address)

Hello Anna-Maria,

On 04/04/2016 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@citrix.com>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: xen-devel@lists.xenproject.org
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.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.
> +	 */
> +
>   	switch (action) {
>   	case CPU_STARTING:
>   		xen_percpu_init();
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1788,6 +1788,13 @@ static int xen_hvm_cpu_notify(struct not
>   			      void *hcpu)
>   {
>   	int cpu = (long)hcpu;
> +
> +	/*
> +	 * Xen guests do not offline/online CPUs during
> +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> +	 * are not considered.
> +	 */
> +
>   	switch (action) {
>   	case CPU_UP_PREPARE:
>   		xen_vcpu_setup(cpu);
> --- a/drivers/xen/events/events_fifo.c
> +++ b/drivers/xen/events/events_fifo.c
> @@ -425,6 +425,12 @@ static int evtchn_fifo_cpu_notification(
>   	int cpu = (long)hcpu;
>   	int ret = 0;
>
> +	/*
> +	 * Xen guests do not offline/online CPUs during
> +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> +	 * are not considered.
> +	*/

NIT: The '*' is not aligned with the others.

> +
>   	switch (action) {
>   	case CPU_UP_PREPARE:
>   		if (!per_cpu(cpu_control_block, cpu))
>

Regards,

-- 
Julien Grall